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Flightline XR

Tach works until battery light goes off

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Alright so I have a 2001 Civic with a manual transmission that started stalling on me on Friday, in motion, after completing a left turn, twice in a row. It would also lose acceleration at a certain RPM and I'd have to shift up to the next gear to be able to keep accelerating, but the tachometer's not reading anything so I couldn't tell you what RPM that is, just that I'd have to be in 3rd in the low 20s mph and 4th in the low 30s etc. Managed to drive it to the mechanic and they told me that the alternator was bad, something about the bolt not being secured correctly after the timing belt repairs I had done a couple months ago.

 

So they went ahead and replaced the alternator for me, but told me that they couldn't get their scanner to communicate with the ECM and recommended I take it to the dealership for diagnostic on that issue. They also wrote "Smells like catalyst is plugged up" on the diagnostic sheet. Of course the dealership is closed until Monday and I have to drive about 30mi to work on Monday where I could just have our on-site mechanic shop look at it ¯\_(ツ)_/¯ (i work at a car auction you see)

 

After replacing the alternator, the problem persisted. No stalling in motion anymore, thankfully, but the loss of power and need to upshift remained, as well as no tach or temp readings. All other electronics seemed to be functioning correctly though. After doing some research online I tried checking a few fuses and resetting the ECM after replacing its fuse (fuse didn't look blown but I figured it couldn't hurt to put a new one in just in case). Started it up, let it idle for 10 mins without touching the accelerator, turned it off and gave it a minute before starting it up again and checking the tach by hitting the accelerator in neutral. It worked fine for a bit and then suddenly stopped, cue huh?????

 

So I turned it off and started it up again and paid attention to the dash lights this time. Idle seems a little unstable but not to the point of sputtering and stalling. Clicking noise from the dash with intermittent CEL on each click (click sounds like it's coming from middle-right side of the dash), battery light on persistently, revved it a few times to confirm tach & temp reading both work. After a minute or so the battery light goes off and the CEL comes on persistent and the tach reading drops off, then the temp reading drops off shortly thereafter. Idle seems to stabilize around this point as well. Drove it around the neighbourhood a bit and it seemed to do okay, where it loses acceleration is much closer to the appropriate mph to be upshifting at now at least.

 

 

TL;DR: New alternator only fixed part of the problem. Battery light on at startup, CEL on intermittent but all dash readings work as normal. Battery light goes off, CEL stays on, tach & temp meters stop working. Loss of power/acceleration in the mid-range mph for the gear, requiring upshift to regain acceleration. Mechanic unable to communicate with ECM for diagnostic codes.

 

So what do you guys think? Battery? ECM? Wiring short? It's not the alternator because that's brand new. I hear a clogged cat can cause issues with engine power but hopefully they're wrong about a problem with the cat because jesus christ do I not want to pay out for that fix.

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