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Stumbling Accelaration, stalls too


James Matteu

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The Problem

 

My car runs fine until the engine warms up; i.e. when the radiator fan comes on. Once warm, it idles steadily at 500RPMs but will intermittently stumble, maybe once or twice every 5 minutes, sometimes not at all. With the motor warm, if I try to rapidly go to Wide Open Throttle (WOT) the motor will stumble as the RPMs increase. Sometimes, the stumbling is really bad and the motor doesn't make it past 1000RPMs, it just stalls out. If the motor makes it past 1000RPMs, the stumbling continues and actually keeps the car from passing 3500RPMs; it just bounces between 3500RPMs and 3250RPMs. While in the 3250-3500RPM zone, if I let up on the throttle slightly, the stumbling disappears and the motor smoothly sails to redline without fail. Releasing the throttle slightly before the 3250-3500RPM zone does not prevent stumbling in the motor's approach to higher RPMs.

 

 

My Car

 

1997 Honda Accord EX-V6 sedan with the C27A4. The C27A4 uses mulit-point Programmed Fuel Injection (PGM-Fi) running On-Board Diagnostics standard 2 (OBD-II). I've got 226732 miles on the body and motor. All stock in the engine bay. I have a 4-speed automatic transmission. I stay on top of all maintenance, and perform all work myself.

 

 

Recent History

 

In the past year, the only unresolved Check Engine Light (CEL) I have gotten was 67: P0420 Catalyst System Efficiency Below Threashold. I've cleared it twice but have not gotten around to finding the cause. I have noticed in the last 3 months my exhaust has taken on a gassy smell which has progressively gotten stronger over those three months. It is as if the amount of unburnt fuel in my exhaust keeps increasing.

 

Florida doesn't have emissions testing and the catalytic converter was replaced in June 2009 with a Magnaflow OEM Replacement; I destroyed the original by leaving a ground wire loose which caused an intermittent power failure in the ECU which lead to backfiring and fuel being dumped into the cat which melted the catalyst. When this new problem arose, I had a third incident of 67 stored in the ECU (yeah, I was driving around with the CEL on).

 

Recent maintenance was done on July 02, 2010:

-5 quarts of Mobile 1 Tri-Synthetic oil

-Honda OEM filter

-Honda Aluminum Drain Plug Crush Washer

-Wearever Silver Brakes in the front

-Resurfaced Brembo OEM Blanks in the front

-Molykote77 on all brake component lubrication points

 

 

My Story

 

Before this started, I was driving with about 3 gallons of 87 octane (up to 10% ethanol content) and decided to fill it up. I used Shell gasoline from 11150 Lem Turner Road, Jacksonville, FL 32218. After about 15 miles of driving, this problem started. I pulled to a red light and without warning, the car simply cut off. I tried to restart the car, it would not start right away. I put on my Hazard Lights, and waived by the traffic behind; yeah, they honked at me. After many attempts, the car finally started; the light was red again. I resolved to mearly pull the car to the side of the road; I was at a four-way intersection. With the car idling fine, I put the car into D and it cut off immediately. I made several attempts to keep the car on while shifting to D, finally it worked when I held the RPMs just past 1000 while shifting into D. The car lunged forward and out of the roadway, but immediately cut off. I checked the dipstick for oil, there was some and it still looked new. I started it back up and sat in my car with it idling for about 10 minutes. I tried reving it a few times and found that it would stumble really bad at WOT, but was incrementally better with less application of throttle. I decided to try and limp it home. With the car idling steadily, I shifted to D with no application of throttle; the car didn't cut off. As soon as I touched the gas, the car shut off. I restared and tried the same trick, no gas, shifted to D, and let the idle speed accelarate the car forward. As soon as the RPMs got around 1100, I gave it a light tap on the gas and the car seemed fine, but I didn't want to push it so I never depressed the gas pedal beyond a slight touch. I drove about 10 miles and came to an intersection where I had to turn left and drive up a steep grade over a bridge. I had a red light and knew the car would not have enough road to build enough speed to get over the bridge after being stopped. While in D and stopped at that red light, the car shut off again. I ended up pushing it to a parking lot at that intersection and having it towed the rest of the way home.

 

 

Observations

 

1. When the motor stumbles, the dash lights do not flicker or fade. There does not seem to be any power failure in the Gauge Cluster or Small Lights Circuit.

 

2. While the car is idling, the Tachometer is steady. It does not blip, or fall, suddenly or unexpectedly.

 

3. When the car was moving, the Speedometer worked fine. It did not loose power or behave irradically.

 

4. I looked for smoke (of any color) to come out of my tailpipe, it never did. I have no strange emissions, just the same gassy smell I mentioned before.

 

5. With the key in the ignition, the Key-In Reminder chime works fine with the door open and giggling the key does not result in any power loss while idling.

 

 

 

Tests

 

1. I pulled the CEL codes and found: 67 and 70.

 

1a. Code 67 represents P0420: Catalyst System Efficiency Below Threashold

This is the same old code that has been sitting in there. I will get back to this at a later date, though I have a feeling that this was the first signs something bad was coming. I may fix this code by resolving my current issue.

 

1b. Code 70 represents P0715, P0720, P0725, P0730, P0740, P0753, and P0758: Automatic Transaxle

Helms sends me to Section 14 for the transmission, but has no suggested causes. I think the motor needs to be fixed first, then I can worry about the transmission. I plan on returning to this code later.

 

I cleared all the CEL codes stored the day this started. I have been working on this in my driveway, but even while reproducing the problem over and over, I have not had any more CEL codes stored since. Note: I have not driven the car anywhere, so the transmission has been out of the equation for now.

 

 

2. Fuel Pressure: I replaced the Banjo Bolt on the Fuel Filter with an adapter so that I could screw in a Fuel Pressure Gauge. Removing the Banjo Bolt relieves the pressure, so the adapter correctly read 0psi when installed.

 

2a. With the car idling and the Fuel Pressure Regulator vaccum hose connected, the pressure is 36.0psi. It should be between 31-38psi, so far so good.

 

2b. With the car idling and the Fuel Pressure Regulator vaccum hose disconnected, the pressure is 44.0psi. It should be between 40-47psi, so 44.0psi is good.

 

2c. With the car stumbling at WOT and the Fuel Pressure Regulator vaccum hose connected, the pressure creaps up to 37.5-38psi. When the car stalls out, the fuel pressure shoots up to 42psi. I guess this is cause with the motor stalled the vaccum supply dies out suddenly and lets the Fuel Pressure Regulator slam shut. So it seems the Fuel Pump is fine, but please let me know if I missed something.

 

 

3. Spark Plugs: I inspected all 6. All looked fine: correct gap, no liquid fuel, no oil, no excessive carbon (soot, black stuff), no excessive metal oxide deposits (white stuff), good center electrode insulator, center electrode still square, not rounded. I noticed that the electrode's arc point was clean and smooth, no pitting or corrosion. All plugs smelled fine though they did have a slight gassy smell. The since my maintenance schedule showed they would be due for a change next month and since I already had the replacements on hand; I went ahead replaced them; all gapped to 1.194mm.

 

 

4. Spark Plug Wires: I measured the resistance across all six. Resistance should be less than 25 kilo-Ohms. The plug wires measured (in kilo-Ohms): #1 17.3, #2 17.0, #3 14.0, #4 9.0, #5 8.0, #6 7.0; so the wires checked out fine.

 

 

5. Distributor Ignition Cap: no cracks, no damage, nor wear on the outside. Inside was clean aside from alittle sand that appears to have blown into it. My Distributor O-ring needs replacing, so I wiped the oil and dirt off the bottom of the outside of the cap and cleaned the points with 1000grit wet/dry automotive sandpaper.

 

 

6. Distributor Ignition Rotor: I inspected the Distributor Ignition Rotor Terminal, it looked fine, no fraying or obvious damage, pitting, or corrosion. With 1000grit wet/dry automotive sandpaper, I cleaned the spot where the cap's carbon point makes contact with the center of the rotor and wiped the distributor's internals clean.

 

 

7. Ignition Control Module: I measured the two volage inputs with the Key in ON. Yellow showed 8 volts, Green showed 8 volts. According to Helms, this means it checks out but please let me know if I missed something.

 

 

8. Ignition Coil: I measured the resistance across the two windings. I didn't worry about the tach output since I never observed any issue with the tach signal at the Gauge Cluster.

 

8a. Resistance across the Primary Winding was less than 0 Ohms; s/b 0.3-.04 Ohms, so far so good.

 

8b. Resistance across the Secondary Winding was 25 kilo-Ohms; s/b 14-22 kilo-Ohms, alittle off spec. When bought this BWD Ignition Coil back in June 2008 the Secondary Winding measured 12 kilo-Ohms, so 25 kilo-Ohms is odd and warrants further investigation.

 

8c. I swapped in a working OEM Ignition Coil (manufactured by TEC) that was pulled off a 1993 Honda Accord. Since the TEC Ignition Coil came from a 4-cylinder ignition system, the tach signal does not work with my tachometer. So it was no suprise that the Tachometer would not function while I was using the TEC. The TEC's Secondary Winding has 19 kilo-Ohms, Primary less than zero. The stumbling problem was not resolved by swapping ignition coils, so I put the BWD back in.

 

 

9. Top Dead Center (TDC) sensor: I measured resistance across the sensor. It should be 1.5-3.0 kilo-Ohms. I found 2.0 kilo-Ohms. According to Helms, this means it checks out but please let me know if I missed something.

 

 

10. Cylinder Position (CYP) sensor: I measured resistance across the sensor. It should be 1.5-3.0 kilo-Ohms. I found 2.9 kilo-Ohms. According to Helms, this means it checks out but please let me know if I missed something.

 

 

11. Air Filter: I inspected it. It was in "new" condition. I brushed off a June Bug and a leaf, and reinstalled the filter.

 

 

12. Throttle Position Sensor (TPS): with the Key in ON I measured voltage on the TPS.

 

12a. I found 4.2 volts on the TPS Reference Voltage (Yellow/Blue: VCC2).

 

12b. I found 0.2 volts at the TPS Output (Red/Black: TPS) while the throttle was in idle position.

 

12c. At WOT, I found 3.8 volts at the TPS Output (Red/Black: TPS).

 

 

13. Throttle Position Sensor (TPS): with the Key removed and with the car off I measured resistance across the TPS:

 

13a. Between the TPS Output (Red/Black: TPS) and TPS Ground (Green/Blue: SG2), I found 0.825 kilo-Ohms at idle; s/b 0.5-0.9 kilo-Ohms, so it looks like I'm good.

 

13b. Between the TPS Output (Red/Black: TPS) and TPS Reference Voltage (Yellow/Blue: VCC2), I found 1.8 kilo-Ohms at idle; s/b approx. 5 kilo-Ohms, I don't know if the TPS is bad. I guess most of the reference is getting back to the ECU at idle, but I thought the ECU stores the output in memory to measure the difference as throttle is applied. Perhaps someone can educate me on this.

 

 

14. Manifold Absolute Pressure (MAP) sensor: I measured voltage at the sensor in several conditions all while it was still connected to the ECU.

 

14a. With the Key in ON, I found 4.3 volts on the reference Yellow/White wire.

 

14b. With the key in ON, I found 2.3 volts on the output White/Yellow wire.

 

14c. With the motor idling at 500RPMs, I found 0.75 volts on the output wire.

 

14d. At WOT, I found the output jumps to about 2 volts but soon settles back down to 0.75

 

14e. After struggling to get the motor to 3000RPMs, I held it there for 60 seconds and then shut it off. I started it back up and I found high vacuum indicated for about a second. Afterwhich, the voltage dropped back to 0.75 volts as the motor idled at 500RPMs. This shows correct operation and rapid response.

 

 

15. Ignition Timing: I used a timing light to check out my timing. The Helms says I should find the Red mark 15 degrees (plus or minus 2 degrees) Below Top Dead Center (BTDC) with the motor idling at 750RPMs. As Helms instructs, I used the SCS Service Connector to connect the Green/Blue and Red terminals on the Service Check Connector (Blue 2-pin connector behind the glove box), and connected the timing light to the battery with the input on the #1 Spark Plug Ignition Wire. I found the red mark to be approx. 13 degrees Below Top Dead Center with the motor idling at 500RPMs, so my timing is good.

 

 

16. PGM-Fi Main Relay: I used a known working unit to replace the one in my car. There was no improvement in the stumbling accelaration.

 

 

17. Positive Crankcase Ventilation (PCV) Valve: I inspected it and found it to be in good working order: plunger not stuck, moves freely, o-ring solid and not cracked.

 

 

18. Intake Air Bypass (IAB): I observed the IAB Control Diaphram Valve allow the IAB to remain open with the car off and then close it with the car on. In WOT, the IAB Control Diaphram correctly opens the IAB at what I percieved to be the correct RPMs (4000), but could not confirm this since I am working by myself and have nobody to apply throttle and observe the tach while I observe the IAB Control Diaphram Valve. With the car off again, I disconnected the IAB Control Diaphram Valve Solenoid. There was no change in the issue at hand with the IAB open at all times.

 

 

19. Ignition Combination Switch: even though I had no indication that my Ignition Combination Switch had or was failing, I swapped in a known working unit from a 1990 Honda Accord EX. I plugged the brown connector at my fuse box and used a flat-head screw driver to start the car. This did not resolve my stumbling accelaration.

 

 

20. Fuel Treatment: I added 16 fluid ounces of Maximum 104+ Octane Boost to my fuel and rocked the car side to side to mix it in with the fuel in there already. This did not resolve my stumbling accelaration.

 

 

 

Things To Do

 

1. Bleed the Cooling System.

 

2. Check the Idle Air Control Valve.

 

3. Check the Crankshaft Position Sensor.

 

4. Check the ECU for damage on the board.

 

5. Check all sensor outputs for good connection to the ECU.

 

5. Check for good connection between the Brake Switch and ECU.

 

6. Remove the Catalytic Converter for visual inspection.

 

7. Find an easy way to test for contaminated fuel.

 

8. Test the Spark Plug Resistor.

 

 

 

Notes

 

1. I called the Shell station and asked if they have had any complaints about their fuel. The lady snapped at me that my insinuation was impossible since they sell nitrogen enriched fuel. I did not acknowledge her deflection and asked what their claims process is. She asked that I call back and speak with the manager. I asked what time he would be in, she said, "In the morning," and hung up on me.

 

2. I did a search on "rough accelaration stalling" and did not find any threads that described an issue exactly like mine.

 

 

 

 

Thank you all for reading and I welcome any comments or suggestions.

 

 

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Holy huge post Batman!

 

Well, just a couple weeks ago I was driving my ancient Jeep a couple hundred miles back from visiting the family for the weekend. It was about 105 that day. I filled up before getting on the highway and about 45 miles down the highway it just shut off at 75mph. Coasted to a stop and nothing I could do would restart the vehicle for more then a moment or two. After sitting for a good 15 minutes I was able to start it up and get up to speed and off at the next exit where it died again. Another 15 minutes went by and started it again and I got it to a Taco Bell lot. Ate dinner and then was able to cover about 30 minutes of highway speed and bam - rinse/repeat all the way the last 60-70 miles home. I could cover about 5-10 and it would die. Wait 15 and do it again. After pondering my predicament for a while on the side of the highway and sweltering my ass off it occured to me that I have had this problem a few times before.

 

The exact symptoms of this are not identical to mine, but the issue sounds very similar. In my case the common factor every time was high heat. Once the tank got to a certain temp it shut off every time. For me getting fuel earlier in the day wasn't my problem though. What it did was introduce cold underground fuel to my fuel tank which had already had significant water in it and delayed the inevitable. Once the tank heated up it died.

 

Bottom line: water in the fuel. The high heat was causing vapor lock. My fix? I burned off about 1/2 tank running short errands around town and then added two quarts of isopropyl rubbing alcohol and filled it the rest of the way up with 94 octane from sunoco. Ran so bad for the first 15 minutes that having it floored to keep it from stalling only netted me 1500-2000 rpms. After 15 it would idle and not die, another 15 and it ran smooth. Never another problem again

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I was looking at the Isopropyl Alcohol products at the store while buying the Octane Boost. I had to make a decision, but obviously picked the wrong one since the octane boost didn't work. You are not the first person tonight to suggest water in the gas, something that hadn't occured to me before due to my misconceptions of the what water would do to an engine. I though water in the gas would make white smoke come out of the tailpipe, since I haven't seen any I figured I didn't have any water in there. You are now the second person with a personal account of water in fuel that describes the same symptoms without a mention of white smoke. This has never happened to me, so I had no idea.

 

I will be pulling a sample of fuel tomorrow to look separation. A fuel treatment for water will follow closely behind.

 

I've also been advised to clean the EGR system thoroughly.

 

Testing for water in the fuel and cleaning the EGR have both been added to my to do list for tomorrow morning.

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In my case I surmise I had no smoke due to the fuel system being entirely locked. When it hit it cut out it was 100% off regardless of current driving/moving status. The good thing is that the alcohol treatment is inexpensive and also functions as a nice fuel system cleanser as a side benefit. My Jeep has a 20 gallon tank I believe. Two quarts is what I used and was suggested to me by a friend that was a certified Chrysler mechanic. Depending on the volume of the tank in your v6 I would adjust the alcohol volume accordingly. It is recommended to replace your fuel filter after performing this treatment. In my case I said to hell with that since I had just replaced it 500 miles earlier and a filter on an old cherokee is a pita on a good day.

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Tests Continued

 

21. Fuel: I disconnected the Fuel Pulsation Damper so that I could pull a 16 ounce (approx.) sample of fuel. I let it sit all afternoon and observed no separation; i.e. no water. This appears to be an issue with my car and not the fuel in it.

 

 

22. Exhaust Gas Recirculation (EGR): I inspected two of the three parts to this system.

 

22a. EGR Chamber: I removed the EGR Chamber Cover and Gasket, all looked in good condition, no excessive build-up of carbon, no plugged holes. I went ahead and cleaned this area with a brass bristle brush, a dental pick, a flathead screwdriver, and a shop vac.

 

22b. EGR Valve: I removed the EGR Valve and found it to be in good condition, no blockages, all passages were clear. I went ahead and cleaned it with a brass bristle brush and flathead screwdriver. I used my vacuum tester to pull vacuum on the EGR Valve to ensure it was able to operate properly. Under vacuum, the valve opens as expected.

 

22c. EGR Tube: I did not remove the EGR Tube from my Rear Exhaust Manifold. Given the condition of the EGR Chamber and EGR Valve, I assume the EGR Tube is not plugged.

 

 

23. Cooling System: I bled the cooling system with the heater set to maximum heat to ensure no air could be trapped in my Idle Air Control Valve (IACV).

 

 

24. Injectors: the injectors were removed for inspection and testing.

 

24a. When I first removed them, I found oil around the part that inserts into the intake manifold. This is the first time I have ever removed them, and have had severe oil leaks in the past so I was not surprised to find oil here. The part where the fuel comes out was immaculate and new in appearance. I suppose that is the part that matters.

 

24b. I used the Memory Circuit to provide voltage via jumper wires to verify correct operation. All six injectors performed flawlessly, the solenoids toggled and skeeted a bit of fuel out when open.

 

24c. All injectors were reinstalled so that I could listen to them click with my stethoscope. I found that when the motor is cold (remember, this is when there is no stumbling) the injectors click with increasing frequency to match the amount of throttle applied. When the motor is warm, at WOT with the motor stumbling its way to bounce between 3250RPMs and 3500RPMs, the injectors click at their idle pace despite the increase in throttle. When I did my trick (blip the throttle from WOT for a second to get the motor past 3500RPMs, see my first post), the injectors came alive and returned to normal operation as the motor sped to redline.

 

 

Hypothesis

 

It’s as if the ECU couldn’t see I opened the throttle. Or it did, and the ECU’s instructions to the injectors were either lost or didn’t make it to the injectors. The latter seems unlikely since the ECU continued to fire the injectors at idle pace.

 

Given today’s findings, I think I need to go back to the Throttle Position Sensor (TPS) and retest it with the motor running. I only tested it with the Key in ON, but not while the motor was running, see my first post, test #12. I want to see what the TPS is telling the ECU when the motor stumbles and I want to see if what the TPS is saying is getting to the ECU. If so, I want to see what the ECU is telling the injectors to do at WOT while the motor is stumbling.

 

Hopefully this means I am coming closer to solving this one.

 

Again, thanks for reading and if anyone has any input, feel free to contribute. Thanks again.

 

 

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I'm just excited to have finally found the approximate cause of my stumbling accelaration. Now it is just a matter of tracing this back to the root cause. I cannot say how excited I was when I put the stethoscope probe against the injector bodies while the car was stumbling and heard them clicking away as if the car was idling; I was all like Ah-HAH! It is so agrivating when you car doesn't run right, but everything you test or look at is fine; given something is obviously not fine.

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From last night...I was tired and went to bed instead of posting.

 

Tests Continued

 

 

Previously…

 

 

 

12. Throttle Position Sensor (TPS): with the Key in ON I measured voltage on the TPS.

 

12a. I found 4.2 volts on the TPS Reference Voltage (Yellow/Blue: VCC2).

 

12b. I found 0.2 volts at the TPS Output (Red/Black: TPS) while the throttle was in idle position.

 

12c. At WOT, I found 3.8 volts at the TPS Output (Red/Black: TPS).

 

 

13. Throttle Position Sensor (TPS): with the Key removed and with the car off I measured resistance across the TPS:

 

13a. Between the TPS Output (Red/Black: TPS) and TPS Ground (Green/Blue: SG2), I found 0.825 kilo-Ohms at idle; s/b 0.5-0.9 kilo-Ohms, so it looks like I'm good.

 

13b. Between the TPS Output (Red/Black: TPS) and TPS Reference Voltage (Yellow/Blue: VCC2), I found 1.8 kilo-Ohms at idle; s/b approx. 5 kilo-Ohms, I don't know if the TPS is bad. I guess most of the reference is getting back to the ECU at idle, but I thought the ECU stores the output in memory to measure the difference as throttle is applied. Perhaps someone can educate me on this.

 

 

 

 

25. Throttle Position Sensor (TPS): with the motor on, I measured voltage on the TPS.

 

25a. Idling at 500RPMs with the motor cold, I found 0.4 volts at the TPS Output (Red/Black: TPS) while the throttle was in idle position.

 

25b. Idling at 500RPMs with the motor cold, I found 4.3 volts on the TPS Reference Voltage (Yellow/Blue: VCC2).

 

25c. With the motor warm, I found 4.3 volts on the TPS Reference Voltage (Yellow/Blue: VCC2) from no throttle (ilding at 500RPMs) all the way to WOT, regardless of whether the motor stumbled or not.

 

25d. With the motor warm, I found 0.3 volts at the TPS Output (Red/Black: TPS) that gradually increased with throttle application, regardless of whether motor stumbled, to a maximum of 3.5 volts at WOT. According to Helms V6 Supplement (page 11-33), my TPS output should be 10% of WOT at idle. So finding 0.3 volt to 3.5 volts is within specs, I guess my TPS is fine but you guys let me know if I missed something.

 

 

26. ECU: I removed the ECU for a visual inspection. All connections appeared good; no broken or bent wires, loose pins, burnt insulation. The board looked good; no dark spots on the bread board, no fried components, I didn’t smell any ozone (a sign of arcing), no dry or cracked solders, no pitting or deterioration to the coating, no broken pins, and nothing loose.

 

26a. I backprobed the ECU’s D Connector pins 6 (Red/Black: TPS) and 22 (Green/Blue: SG2) so that I could repeat test #25d. I found the same results, so the ECU is receiving the correct voltages from the TPS.

 

26b. I did not backprobe the Injector connections as I had hoped to do. Upon further review of the circuit diagram, I realized all I would see is constant voltage on all six connections since positive voltage runs from the PGM-Fi Main Relay (see test #16) through the Injector Resistor to all the Injectors. The ECU uses six transistors to switch on and off each Injector’s connection to ground. My multimeter cannot measure large currents (over 250mA), so I cannot watch the Injectors function through my meter.

 

 

Notes

 

I feel I’ve either missed something or overlooked something obvious. I think I should return to the recent history and investigate the CEL code 67. My exhaust is hot from testing. Tomorrow, after cooling overnight, I will remove my Catalytic Converter and make a visual inspection, then move onto the Oxygen (O2) Sensors. I will likely return to test #26 as various connections to the ECU are inspected.

 

 

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25d. With the motor warm, I found 0.3 volts at the TPS Output (Red/Black: TPS) that gradually increased with throttle application, regardless of whether motor stumbled, to a maximum of 3.5 volts at WOT. According to Helms V6 Supplement (page 11-33), my TPS output should be 10% of WOT at idle. So finding 0.3 volt to 3.5 volts is within specs, I guess my TPS is fine but you guys let me know if I missed something.

 

 

From what you say you are correct, it looks fine.

Edited by j_link
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Just an idea; you might try looking into your Cam/Crank position sensor. It might have affect on the system. If its not reading right might not pulse injectors properly.

Edited by j_link
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Tests Continued

 

Previously…

 

9. Top Dead Center (TDC) sensor: I measured resistance across the sensor. It should be 1.5-3.0 kilo-Ohms. I found 2.0 kilo-Ohms. According to Helms, this means it checks out but please let me know if I missed something.

 

 

10. Cylinder Position (CYP) sensor: I measured resistance across the sensor. It should be 1.5-3.0 kilo-Ohms. I found 2.9 kilo-Ohms. According to Helms, this means it checks out but please let me know if I missed something.

 

 

 

27. Crankshaft Position (CKP) Sensor: I measured resistance across the sensor. It should be 1.8-2.5 kilo-Ohms. I found 1.54 kilo-Ohms. According to Helms, this means it’s out of spec, but not by much. What do you guys think? I have found components slightly out of spec and still working fine.

 

 

 

 

28. Catalytic Converter: I removed it for inspection. I remember when I installed this Magnaflow OEM spec Catalytic Converter back in June 2009; I could see through the screen, it had no obstructions. Today, I found small pellet looking things all over the screen and a rattling sound when I shook it. Take a look everyone; is this enough obstruction to trigger CEL code 67? I think so. I was very upset when I started the car without the Catalytic Converter in hopes of discovering my problem went away; it did not. Removing the Catalytic Converter did not resolve the stumbling acceleration.

 

(For some reason, the forum isn't letting me insert images. Come back later, I will try again tomorrow)

 

http://i268.photobucket.com/albums/jj7/Js2d355jf69lsd/Cat001.jpg

 

http://i268.photobucket.com/albums/jj7/Js2d355jf69lsd/Cat002.jpg

 

 

 

 

29. Oxygen Sensors: I removed both for inspection: I found the secondary sensor had some damage. Both heating elements otherwise checked out. See below, should I replace?

 

 

 

http://i268.photobucket.com/albums/jj7/Js2d355jf69lsd/OxygenSensors001.jpg

 

http://i268.photobucket.com/albums/jj7/Js2d355jf69lsd/OxygenSensors002.jpg

 

 

30. Injector Resistors: I measured ZERO ohms on all resistors. According to Helms V6 Supplement page 11-110, there should be 5-7 ohms across all of them. Could this be the cause of my injectors firing slowly?

 

 

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that catalytic converter certainly is a bit clogged. that may be causing some issues, just not the primary it appears.

 

the oxygen sensors certainly look fine. i suppose a quick check for them would be to reverse the positions if the sensors themselves are identical. see if the error changes for you.

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27. Crankshaft Position (CKP) Sensor: I measured resistance across the sensor. It should be 1.8-2.5 kilo-Ohms. I found 1.54 kilo-Ohms. According to Helms, this means its out of spec, but not by much. What do you guys think? I have found components slightly out of spec and still working fine.

 

 

You may be right that it is fine even out of spec. But think of this; the range that Helms stats is 1.8-2.5 which is only a difference of .7 kilo-Ohms. Your sensor is .26 below that spec. That is %20 below the range of operation. Not sure if its what is causing the problem but since you ran the motor agin, check the sensor again and see if there is any change in reading.

 

Also i see the hole in the O2 sensor, I would replace, but in this case thats just me. Not sure if it is bad but if you can switch them like Xeryon stated.

 

As far as the cat is concerned, yes it is bad. But what ever is going on in the motor i think is what caused it to go bad.

 

I am not sure if you covered this in your repairs so far, but have you checked the passage on the intake manifold for the EGR to see if it was restricted? If I missed it i'm sorry.

Edited by j_link
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'Xeryon', I cannot switch around the Secondary and Primary Heated Oxygen Sensors, the wires are not long enough and I have no way of insulating jumper wires; they would melt on the exhaust.

 

'j_link', I forgot to recalibrate my analog multimeter for kilo-Ohms and generated false data. See below, I retested the Crankshaft Position (CKP) Sensor and found it to be within specs. I agree that the Catalytic Converter likely failed due the problem I am chasing rather than the cat being the cause, especially given that the problem has persisted despite my removing the cat from the exhaust. All testing after the cat inspection has been done with the cat removed (I'm sure my neighbors are getting real tired of all the noise). And yeah, I checked the EGR passages at the Intake Manifold and found them to be free of restriction; I cleaned what little carbon was there since I had it open.

 

I still have no CELs that are not related to my removing the catalytic converter and both O2 sensors with it. I haven't figured out a good way to test the injectors.

 

 

 

Tests Continued

 

 

 

Previously...

 

7. Ignition Control Module: I measured the two voltage inputs with the Key in ON. Yellow showed 8 volts, Green showed 8 volts. According to Helms, this means it checks out but please let me know if I missed something.

 

7a. I checked for an open circuit between the Ignition Control Module (ICM), Connection #110 (C110), and ECU Alpha Connector, Connection #458 (C458). I found zero Ohms between C458 pin 11 and C110 pin 2 (Yellow/Green).

 

 

 

9 (retest). I recalibrated my analog multimeter and tested the TDC Sensor. I found 2.4 kilo-Ohm resistance across the TDC Sensor. It should be 1.5-3.0 kilo-Ohms, 2.4 is within spec.

 

9a. I checked for an open circuit between the TDC Sensor, Connection #109 (C109), and the ECU Bravo Connector, Connection #459 (C459). I found zero Ohms between:

C459 pin 7 and C109 pin 1 (Green),

C459 pin 15 and C109 pin 2 (Red).

 

9b. I checked for a short to ground between the TDC Sensor and ECU. I disconnected C109 and found infinite Ohms between ground and either C459 pin 7 (Green) or C459 pin 15 (Red).

 

9c. I retested the TDC Sensor through C459 at the ECU. With C109 connected, I found 2.5 kilo-Ohms between C459 pin 15 (Red) and pin 7 (Green). I found the increase in resistance odd when compared to other sensor circuits, but it's still within spec.

 

9d. I checked for a short to ground inside the TDC Sensor. I found infinite Ohms between ground and either C109 pin 1 or C109 pin 2.

 

 

 

10 (retest). I recalibrated my analog multimeter and tested the CYP Sensor. I found 2.3 kilo-Ohm resistance across the CYP Sensor. It should be 1.5-3.0 kilo-Ohms, so 2.3 is within spec.

 

10a. I checked for an open circuit between the CYP Sensor, Connection #109 (C109), and the ECU Bravo Connector, Connection #459 (C459). I found zero Ohms between:

C459 pin 6 and C109 pin 3 (Yellow),

C459 pin 14 and C109 pin 4 (Black).

 

10b. I checked for a short to ground between the CYP Sensor and ECU. I disconnected C109 and found infinite Ohms between ground and either C459 pin 6 (Yellow) or C459 pin 14 (Black).

 

10c. I retested the CYP Sensor through C459 at the ECU. With C109 connected, I found 2.5 kilo-Ohms between C459 pin 14 (Black) and pin 6 (Yellow).

 

10d. I checked for a short to ground inside the CYP Sensor. I found infinite Ohms between ground and either C109 pin 3 or C109 pin 4.

 

 

 

Previously...

 

13. Throttle Position Sensor (TPS): with the Key removed and with the car off I measured resistance across the TPS:

 

13a. Between the TPS Output (Red/Black: TPS) and TPS Ground (Green/Blue: SG2), I found 0.825 kilo-Ohms at idle; s/b 0.5-0.9 kilo-Ohms, so it looks like I'm good.

 

13b. Between the TPS Output (Red/Black: TPS) and TPS Reference Voltage (Yellow/Blue: VCC2), I found 1.8 kilo-Ohms at idle; s/b approx. 5 kilo-Ohms, I don't know if the TPS is bad. I guess most of the reference is getting back to the ECU at idle, but I thought the ECU stores the output in memory to measure the difference as throttle is applied. Perhaps someone can educate me on this.

 

13 (retest). I recalibrated my analog multimeter and retested the TPS.

 

13a/b (retest). I checked for an open circuit within the TPS. With the Key removed, car off, and TPS in idle position, I measured resistance across the TPS and found:

0.825 kilo-Ohms between the TPS Output and TPS Ground; s/b 0.5-0.9 kilo-Ohms.

7.0 kilo-Ohms between the TPS Output and TPS Reference Voltage; s/b approx. 5 kilo-Ohms.

 

13c. I checked for a short to ground between the TPS and ECU. I disconnected the TPS, Connection #111 (C111), and found infinite Ohms between ground and either C111 pin 2 (Red/Black) or pin 1 (Green/Blue).

 

13d. I checked for a short to ground in the TPS. When tested individually, I found infinite resistance between ground and all three sensor pins.

 

13e. I checked for an open circuit between C111 and ECU Delta Connector, Connection #460 (C460). I found zero Ohms of resistance between:

C460 pin 22 and C111 pin 1 (Green/Blue),

C460 pin 6 and C111 pin 2 (Red/Black),

C460 pin 21 and C111 pin 3 (Yellow/Blue).

 

I've already tested TPS function at C460...

 

25d. With the motor warm, I found 0.3 volts at the TPS Output (Red/Black: TPS) that gradually increased with throttle application, regardless of whether motor stumbled, to a maximum of 3.5 volts at WOT. According to Helms V6 Supplement (page 11-33), my TPS output should be 10% of WOT at idle. So finding 0.3 volt to 3.5 volts is within specs, I guess my TPS is fine but you guys let me know if I missed something.

 

26a. I backprobed the ECU's D Connector pins 6 (Red/Black: TPS) and 22 (Green/Blue: SG2) so that I could repeat test #25d. I found the same results, so the ECU is receiving the correct voltages from the TPS.

 

 

 

Previously...

 

14. Manifold Absolute Pressure (MAP) sensor: I measured voltage at the sensor in several conditions all while it was still connected to the ECU.

 

14a. With the Key in ON, I found 4.3 volts on the reference Yellow/White wire.

 

14b. With the key in ON, I found 2.3 volts on the output White/Yellow wire.

 

14c. With the motor idling at 500RPMs, I found 0.75 volts on the output wire.

 

14d. At WOT, I found the output jumps to about 2 volts but soon settles back down to 0.75

 

14e. After struggling to get the motor to 3000RPMs, I held it there for 60 seconds and then shut it off. I started it back up and I found high vacuum indicated for about a second. After which, the voltage dropped back to 0.75 volts as the motor idled at 500RPMs. This shows correct operation and rapid response.

 

14f. I checked for an open circuit between the MAP Sensor, Connection #118 (C118), and ECU Delta Connector, Connection #460 (C460). I found zero Ohms between:

C460 pin 10 and C118 pin 1 (Yellow/White),

C460 pin 11 and C118 pin 2 (Green/White),

C460 pin 9 and C118 pin 3 (White/Yellow).

 

14g. I checked for a short to ground between the MAP Sensor, C118, and ECU, C460. With C118 disconnected, I found infinite Ohms between ground and:

C460 pin 10,

C460 pin 11,

C460 pin 9.

 

14h. I checked for a short to ground in the MAP Sensor. When tested individually, I found infinite resistance between ground and all three sensor pins.

 

 

 

Previously...

 

21. Fuel: I disconnected the Fuel Pulsation Damper so that I could pull a 16 ounce (approx.) sample of fuel. I let it sit all afternoon and observed no separation; i.e. no water. This appears to be an issue with my car and not the fuel in it.

 

21a. I defueled my fuel tank and refueled with fresh E10 gas (rated at 87 octane, M+S method) from another gas station. I did this despite not finding any wet gas, free water, or particulates, in the sample I pulled the other day.

 

 

 

Previously...

 

22. Exhaust Gas Recirculation (EGR): I inspected two of the three parts to this system.

 

22a. EGR Chamber: I removed the EGR Chamber Cover and Gasket, all looked in good condition, no excessive build-up of carbon, no plugged holes. I went ahead and cleaned this area with a brass bristle brush, a dental pick, a flathead screwdriver, and a shop vac.

 

22b. EGR Valve: I removed the EGR Valve and found it to be in good condition, no blockages, all passages were clear. I went ahead and cleaned it with a brass bristle brush and flathead screwdriver. I used my vacuum tester to pull vacuum on the EGR Valve to ensure it was able to operate properly. Under vacuum, the valve opens as expected.

 

22c. EGR Tube: I did not remove the EGR Tube from my Rear Exhaust Manifold. Given the condition of the EGR Chamber and EGR Valve, I assume the EGR Tube is not plugged.

 

22d. I checked for an open circuit between the EGR Lift Sensor, Connection #129 (C129), and the ECU Delta Connector, Connection #460 (C460). I found zero Ohms between:

C460 pin 17 and C129 pin 1 (White/Black),

C460 pin 22 and C129 pin 2 (Green/Blue),

C460 pin 21 and C129 pin 3 (Yellow/Blue).

The EGR Valve Lift Sensor sits atop the EGR Valve, detects the amount of EGR valve lift, and sends the info to the ECU. The ECU compares that data with the ideal* EGR Valve lift it has stored in memory. The ECU then adjusts current to the EGR Control Solenoid Valve to change the amount of vacuum applied. *Ideal EGR Valve Lift is calculated using signals received from the ECU sensor array.

 

22e. I checked for an open circuit between the EGR Control Solenoid, Connection #270 (C270), and ECU Alpha Connector, Connection #458 (C458). I found zero Ohms between C458 pin 9 and C270 pin 2 (Red).

 

22f. I checked for an open circuit between the EGR Control Solenoid, C270, and the common ECU solenoid power source: Fuse #4 (7.5A). I found zero Ohms between C270 pin 1 (Black/Yellow) and Fuse #4.

 

22g. I checked for a short to ground between the EGR Control Solenoid, C270, and ECU, C458. With C270 disconnected, I found infinite Ohms between C458 pin 9 and ground.

 

22h. I checked for a short to ground in the EGR Lift Sensor. When tested individually, I found infinite resistance between ground and all three sensor pins.

 

22i. With the car idling at 500RPMs and warm, vacuum to the EGR Valve measured at 0 mmHg. This indicates the EGR Control Solenoid is ungrounded by the ECU during idle.

 

22j. I backprobed C458 pin 9 so that I could manipulate the EGR Control Solenoid. With ground applied via the backprobe, the car idling at 500RPMs, and motor warm, vacuum to the EGR Valve measured 180 mmHg. Helms says there s/b approx. 200 mmHg, so 180 is within spec, approximately.

 

22k. With the car idling at 500RPMs and warm, I applied 200 mmHg to the EGR Valve. The car stalled and the EGR Valve held vacuum, this is within spec. This also confirms that the EGR Tube is clear.

 

22l. I held throttle at WOT. When the motor stumbled to 3500RPMs and would go no higher, I grounded the EGR Control Solenoid so that the EGR Valve would open completely. This did not prevent the stumbling nor get the motor past 3500RPMs.

 

 

 

Previously...

 

27. Crankshaft Position (CKP) Sensor: I measured resistance across the sensor. It should be 1.8-2.5 kilo-Ohms. I found 1.54 kilo-Ohms. According to Helms, this means it's out of spec, but not by much. What do you guys think? I have found components slightly out of spec and still working fine.

 

27 (retest). I recalibrated my analog multimeter and retested the CKP Sensor. I found 2.4 kilo-Ohm of resistance across the CKP Sensor, this is within spec.

 

27a. I checked for a short to ground in the CKP Sensor. I found infinite resistance between ground and either sensor pin.

 

27b. I checked for a short to ground between the CKP Sensor, Connection #133 (C133), and Engine Control Unit (ECU) Bravo Connector, Connection #459 (C459). With C133 disconnected, I found infinite Ohms between ground and both:

C459 pin 8 (Blue),

C459 pin 16 (White).

 

27c. I checked for an open circuit between the CKP Sensor, C133, and ECU, C459. I found O Ohms of resistance between:

C459 pin 8 and C133 pin 1 (Blue),

C459 pin 16 and C133 pin 2 (White).

 

27d. I retested the CKP Sensor through C459 at the ECU. With C133 connected, I found 2.5 kilo-Ohms between C459 pin 8 (Blue) and pin 16 (White).

 

 

 

Previously...

 

29. Oxygen Sensors: I removed both for inspection: I found the secondary sensor had some damage. Both heating elements otherwise checked out. See below, should I replace?

 

29 (retest). I retested the Primary and Secondary Heated Oxygen Sensors and found:

Primary Heated Oxygen Sensor's Heating Element = 11 Ohms,

Secondary Heated Oxygen Sensor's Heating Element = 7 Ohms;

where they should be between 10-40 Ohms. I am going to replace the Secondary, but am contemplating replacing the Primary as well. I have continued testing without the Catalytic Converter on the car.

 

 

 

Previously...

 

30. Injector Resistors: I measured ZERO ohms on all resistors. According to Helms V6 Supplement page 11-110, there should be 5-7 ohms across all of them. Could this be the cause of my injectors firing slowly?

 

30 (retest). Since the results of my last test did not make any sense, I recalibrated my analog multimeter and retested the Injector Resistors. I found:

resistor 1 = 5.90 Ohms,

resistor 2 = 5.90 Ohms,

resistor 3 = 5.85 Ohms,

resistor 4 = 5.90 Ohms,

resistor 5 = 5.90 Ohms,

resistor 6 = 5.90 Ohms;

where Helms states there should be 5-7 Ohms, the Resistor Box is good.

 

 

 

32. Intake Air Temperature (IAT) Sensor: a thermistor whose resistance decreases as the intake air temperature increases.

 

32a. I took a reading at the IAT Sensor to see if it was giving erroneous data to the ECU. According to Helms, at 92° F (ambient temp for the day I ran this test) the sensor have approx. 1 kilo-Ohm of resistance, but the chart is small and therefore my interpretation of it is inaccurate. Additionally, I am unable to factor in things such as the car sitting in shade, etc. However, the car sat overnight and had not been started yet (cold), so it should give the same reading as the Engine Coolant Temperature (ECT) Sensor. I measured resistance across the IAT Sensor and found 1.20 kilo-Ohms; see test #33a.

 

32b. I checked for an open circuit between the IAT Sensor, Connection #131 (C131), and ECU Delta Connector, Connection #460 (C460). I found zero Ohms between:

C460 pin 22 and C131 pin 1 (Green/Blue),

C460 pin 8 and C131 pin 2 (Red/Yellow).

 

32c. I checked for a short to ground between the IAT Sensor, C131, and ECU, C460. With C131 disconnected, I found infinite Ohms between ground and:

C460 pin 8,

C460 pin 22.

 

32d. I checked for a short to ground in the IAT Sensor. I found infinite resistance between ground and either sensor pin.

 

32e. I retested the IAT Sensor through C460 at the ECU. With C131 connected, I found 1.20 kilo-Ohms between C460 pin 22 (Green/Blue) and pin 8 (Red/Yellow).

 

 

 

33. Engine Coolant Temperature (ECT) Sensor: a thermistor that decreases resistance to the reference voltage as a function of the coolant temperature.

 

33a. I measured resistance across the ECT Sensor and found 1.19 kilo-Ohms; see test 32.

 

33b. I checked for an open circuit between the ECT Sensor, Connection #113 (C113), and ECU Delta Connector, Connection #460 (C460). I found zero Ohms between:

C460 pin 22 and C113 pin 1 (Green/Blue),

C460 pin 7 and C113 pin 2 (Red/White).

 

33c. I checked for a short to ground between the ECT Sensor, C113, and ECU, C460. With C113 disconnected, I found infinite Ohms between ground and:

C460 pin 7,

C460 pin 22.

 

33d. I checked for a short to ground in the ECT Sensor. I found infinite resistance between ground and either sensor pin.

 

33e. I retested the ECT Sensor through C460 at the ECU. With C113 connected, I found 1.19 kilo-Ohms between C460 pin 22 (Green/Blue) and pin 7 (Red/White).

 

 

 

35. I checked for a short to ground between the Service Check Connector, Connection #454 (C454), and ECU, C460. With C454 open, I found infinite Ohms between ground and C460 pin 22.

 

 

 

36. Evaporative Emission (EVAP) Control:

 

36a. I checked for an open circuit between the EVAP Purge Flow Switch, Connection #270 (C270), and ECU Alpha Connector, Connection #458 (C458). I found zero Ohms between C270 pin 3 (Brown) and C270 pin 24. I checked for an open circuit between C270 pin 4 (Black) and ground, I found zero Ohms.

 

36a. I checked for a short to ground between the EVAP Purge Flow Switch, C270, and ECU, C458. I found infinite Ohms between ground and C458 pin 24.

 

 

 

37. Fast Idle Thermo Valve (FITV): I removed the Air Cleaner (ACL) Housing Cover and Intake Air Duct to inspect the FITV.

 

37a. With the engine idling cold at 1100RPMs, I put my finger over the FITV inlet. I could feel air flow into the FITV inlet, and when I completely covered the inlet the idle dropped.

 

37b. With the engine idling warm at 500RPMs, I put my finger over the FITV inlet. I could feel a slight vacuum, nothing like the draw of air I felt when the motor was cold. When I plugged the FITV inlet with my finger, the idle did not drop.

 

 

 

38. Idle Air Control Valve (IACV): I removed the ACL Housing Cover and Intake Air Duct to inspect the IACV.

 

38a. With the engine idling cold at 1100RPMs, I put my finger over the IACV inlet. I could feel air flow into the IACV inlet, and when I completely covered the inlet the idle dropped.

 

38b. With the engine idling warm at 500RPMs, I put my finger over the IACV inlet. I could feel air flow into the IACV inlet, and when I completely covered the inlet the motor stalled. This also indicates the Throttle Body Valve does make a good seal and does not have any significant air leakage.

 

 

 

Observations

 

I took some videos on my phone. The resolution is low, but this was the only way to capture video with sound and post it up. The exhaust is loud because I still have the catalytic converter removed.

 

With the engine warm, if I feather the throttle, I can accelerate smoothly. I have similar performance on a cold motor.

 

http://s268.photobuc...ottlesmooth.mp4

 

When the engine is warm, flooring it (WOT applied quickly) causes it to stumble. When the RPMs reach 3500, the motor is unable to go any faster unless I let up on the throttle (slightly less than WOT).

 

http://s268.photobuc...3500RPMwall.mp4

 

Sometimes, I floor it and the motor stumbles bad enough to stall.

 

http://s268.photobuc...rrent=stall.mp4

 

At the throttle body, I have trouble opening it to WOT quickly enough to reproduce the issue, but you can see at the end I succeed. This is how I listened to the injectors while reproducing the problem. Again, when it stumbles, the injectors keep ticking away at the same frequency as idle.

 

http://s268.photobuc...t=EngineBay.mp4

 

 

HELP!excl.gif

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I am going to go back to the cat and o2 sensor. On Tuesday we had a Toyota truck come in with a similar problem. They took the cat out and put in a straight pipe (because they were told cat was bad). later that week they complained of the same issue, works good at light throttle, but if they get on it, it stalls out or won't climb on RPM, i think in this case it was 2500RPM. After installing a Cat and replacing the O2 sensors the problem went away. Don't know if this will be the same result for you but its an idea.

 

29. Oxygen Sensors: I removed both for inspection: I found the secondary sensor had some damage. Both heating elements otherwise checked out. See below, should I replace?

 

 

 

From a few mechanics I have talked to, they have pointed me to O2 sensors.

 

We already know the Cat is bad, but lets think about this for a sec. You said that the secondary O2 looked damaged, but you said it checked out. How did you check it?

1b. Code 70 represents P0715, P0720, P0725, P0730, P0740, P0753, and P0758: Automatic Transaxle

Helms sends me to Section 14 for the transmission, but has no suggested causes. I think the motor needs to be fixed first, then I can worry about the transmission. I plan on returning to this code later.

 

 

I read up a little on your car in alldata and found that the P0420 can have an effect on the transmission, how I’m not sure yet. I am trying to confirm today if these codes where in the info i read and how they could be affected, I will get back to you on this.

 

 

In the current state you have removed the cat and thus the secondary O2 sensor is not changing. This might be causing the computer to not adjust the fuel injector pulse for WOT the same way a bad sensor could trick it also. Under light throttle application the computer may think that the little reading change or lack of that in the O2 is normal, but under WOT the computer may think I’m getting to lean/rich because i should of seen a change in the secondary O2 but I didn't.

 

4. I looked for smoke (of any color) to come out of my tailpipe, it never did. I have no strange emissions, just the same gassy smell I mentioned before.

 

 

As im sure you know this tells of a rich fuel mixture, which could be what the slow pulse width on the injectors that you hear is caused by false info from the O2 sensor.

Edited by j_link
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What I checked was the Oxygen Sensor Heating Element. Helms has input tests for the O2 Sensor, but that only measures voltage from the ECU. Output from the O2 has to be done through the OBD-II connector, I don't have that capability just yet. I double checked the Secondary Oxygen Sensor (the damaged one) and found it to be out of spec; my multimeter needed to be re-zeroed.

 

I have a guy driving his 1997 Honda Accord LX-V6 over to my house this weekend, we will swap ECUs and see if the problem is affected. If not, I'm changing the O2s, catalytic converter and going from there.

 

Changed so far:

Ignition Control Module - replaced with known working unit

PGM-Fi Main Relay - replaced with known working unit

Spark Plugs - replaced with new

Fuel - replaced with new

Ignition Coil - replaced with known working unit, but swapped back old.

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Holly cow Batman, I was not able to read all the postings but one thing that I did notice is that when you let off the throttle the engine will accelerate, or atleast that is what is sounded like while skimming through the posts. If that is the case then I would consider replacing the fuel filter as engine accaleration upon removing your foot from the pedal can, and is often caused by a clogged fuel filter. Just something to think about.

 

Things that can also cause missfire or rough running are 1) a faulty fuel injector, 2) injector resistor and 3) fuel pressure regulator in that order (but you know that already. I would also consider swapping the MAP from the car that is coming to see if that does the trick. Also, did you test the engine temperature sensor? If that goes bad and with the engine hot the car make think that the temp is cool thus trying to adjust the air/fuel ratio thinking the car needs to warm up. I would also test the EGR by disconnecting the hose to the top of the valve with the car running at idle and 1) see if it hase vaccum to that hose and 2) connect the vaccum pump to the EGR valve and apply 8 in Hg of vac to the valve. The engine should run rough or stall, if it does not then replace or swap the EGR vavle out. I am also wondering at little about the IACV. Check all your vaccum lines for cracks and listen to each line carefully with the engine at idle and listen from a faint "sipping" sound.

 

Sorry to hear about your woes James. Keep us posted.

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Ok, I was able to confirm that the code 67 can also cause the code 70 based on my reading in alldata. Now that we know your O2 is bad, I am really thinking this might be the source of your problem. Keep us posted on if the ECU fixes your troubles though.

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Thanks 'j_link', that's good to know. If I kill two birds with one stone, I will be so happy.

 

Glad to see you here 'Turtlehead'! Thanks for the suggestions! I have a fuel pressure gauge mounted to the low side of the Fuel Filter, the pressure is within spec, even during stalling/stumbling. At my job (chemical plant), all our filtration systems are evaluated this way, so I know the methodology is sound. Would you suggest replacing it anyways? All injectors were wiped clean, bench tested, and reinstalled. All injector resistors have resistances that are in spec. The Fuel Pressure regulator also checked out; without vacuum, fuel pressure rose into the low- to mid-forties. My Coolant Temp Sensor and Air Temp Sensor both agree while the motor is cold. I have not removed either for independent calibration, though their agreement is sufficient at this time. I will test them again through the ECU (see below). Both EGR and IACV checked out; the EGR was extensively tested since I had hoped this was the cause of my misery and woe. My last Accord was an A20 powered LX that used the CVCC system, so I have extensive experience with what a vacuum leak sounds like and I am sorry to say I have none; sorry cause I have about 20 feet of stock vacuum line left over from my CVCC days. My guy cannot come until next weekend, so I don't have a MAP Sensor or ECU to swap just yet.

 

I am looking at buying OBD-II software so that I can connect my computer to my ECU and trend all data being received from the sensor array.

 

Would you be able to suggest a good brand, or company?

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I'll get back to you on the OBD-II conversion question (you have, if I recall, a CL dash assembly), but for now, yes, I would replace your fuel filter. It seems like such a rudimentary item, but it can cause your issue, and once replaced it should not have to be replaced again (atleast for another 200K unless bad fuel is used). FYI, you should be measuring the fuel pressure after the filter on the rail. There should be a fuel pressure relief port on the rail that also allows you to connect a pressure gauge to. Typically it is near the banjo fitting on the rail, but not always. I would think about replacing the fuel filter if it were me. They are life time filters, but who determines life time... I am not saying that it is as simple as replacing the filter, but one of the main causes of your problem could be that. It sounds like you have put a lot of time into this issue and I am only trying to get you closer to the potential cause. Previous posts mention the O2 sensors, which it could be, but on your generation due to the lower techknowlogy (OBD-I) this is less likely to cause your issue since the system is less sensitive. BUT, because you have an aftermarket CAT on the car, if it were to begin failing the O2 sensors may throw faulty signals to the ECM thus increasing the fuel load to the engine and cause studdering (a.k.a. faulty ignition). I woudl also take a large diameter hose piece and place it to your ear and listen to each injector. You should hear a slight clicking sound on each. If the injector lifter(s) is stuck you will not hear the clicking sound, and simply cleaning/wiping the injector tip is not enough to get it working again. If it is an injector you may want to run the fuel tank down and put some liquid BG44K fuel system cleaner in it.

 

Let us know how you make out. Turtlehead...

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All 1995-1997 Accord V6s run OBD-II. I want to buy a software that can datalog my sensor array, like below.

 

I have my fuel pressure gauge on the relief bolt, just as you described. I will go ahead and change it out anyways.

 

I listened to the injectors with an automotive stethoscope, I found they operate at all times, even when the problem occurs though I noticed the frequency of clicking remains low during the stumbling.

 

graphV6.jpg

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Sorry James, I was under the impression that you were driving a 95 V6 pre-1996 OBD-II. I just re-read your original post and you have a 1997. I will re-read things and se what I can provide. I would however, manually test the entire ignition system for arc (cap, wires, coil etc.). It does sound like and ignition issue.

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I think the universe is telling me to recheck the TPS...

 

I keep trying to figure out why I can manipulate this problem with the throttle, then my cousin calls and asked me to help him fix his girlfriend's Civic; he tells me she has a CEL for the TPS. Her Civic was doing everything my car is doing except she gets a CEL for the TPS. I do a search on TPS issues on all makes and find story after story of people that have the same problems as I, some get CELs some don't. Then I find one site where a guy explains why the ECU may be fooled into thinking the TPS is fine when it is not. He says the contacts inside the potentiometer may be damaged enough to create RF noise in the ECU Sensor input, but not interupt the reference voltage long enough to register an error. He also explained how to replace a TPS without having to replace the throttle body (phew!). Furthermore, he explains that the way an analog meter uses EMF to move the needle can often hide the intermittently failing TPS if voltage is being read. He says a digital meter can also be fooled if the bad spots are small. This would explain why I see no problem with the TPS while looking at voltage, and I've never checked the resistance of the TPS while in operation, only at idle. He says to view the RF distortion, an osciliscope or other device that can trend voltage over small increments of time must be used. Good thing I have my OBD-to-USB cable on the way, I just have to find a program that can log the COM ports over milli-seconds.

 

In a related matter, nobody (BLOX, Omni, Yonaka, Blackworks) stocks a TPS for my C27. I will be in contact with them next week to see about providing my specs and having one matched or made (may be cheaper to replace the throttle body if they have to make it).

 

The aforementioned "guy" did mention being able to open the TPS and clean the wipers, but expressed a lack in confidence over the efficacy of such a repair.

 

Tomorrow, I will retest the TPS looking for resistance in all throttle positions, I may be able to see the needle flutter if the there is a bad spot among the wiper contacts.

Edited by James Matteu
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