I bought a 1995 Del Sol S 1.5l (d15b7) in October. It is completely stocked and in very good condition, with only ~145k miles. The previous owner bought it from a kid about fifteen years ago and garaged it, only driving it occasionally during the summer. The only modifications that have been done (to my knowledge) are a cold air intake and aftermarket rims.
Problems - For some reason, when the car is revved to 4k, the needle will sort of bounce off of the 4k mark as if it is being limited, and black smoke will shoot out of the exhaust and pop like the engine is backfiring. The exhaust smells like gasoline and I only get around 20 MPG when I should be getting around 40. The car will also idle anywhere from 1-2k, sometimes just bouncing around in between. This all sounds quite bad but it runs very well besides this issue. It doesn't affect the overall performance or ride beside a funny idle and not being able to go past 4k. It is very mechanically sound and has no rust or zero other issues besides these, hes just a little special needs, still, very fun to drive.
The previous owner of the car did not know much about Del Sols or cars in general. I assume they only had it because they liked how the top came off and just wanted something that looked cool to drive during the summer. He was not aware of the issue, I assume he never even pushed it past 4k to begin with so I have no idea when this problem began or why.
Things I have tried:
New Sensors - New MAP and IAT Sensor, nothing changed.
ECU - The ECU that came with the car is from a 93' Del Sol, which is written in the green market on the top. When I opened the ECU up to take a look, I found that about 1/4 of one of the PCBs was visibly damaged/fried. So of course I went online and purchased a brand-new ECU. I purchased it from a company called Flagship which supposedly tuned exactly to my VIN which I provided. Upon installing the new ECU, the car would just crank and never turn over no matter how long I tried. I haven't returned the ECU or contacted the company as I have been busy but I am planning to do that soon.
Engine Code - The car will not throw a code with the ECU it came with. When the new ECU was installed, I got it to throw a code, although it threw a code for the exhaust gas recirculation system, which to my knowledge does not exist on D-Series. Very confusing.
Inspection - Got the car inspected, mechanics looked at it inside and out and saw no visible issues, they even said it was in spectacular condition for the year. When I asked about the issue, they said "It's definitely a rev limiter" even though the stock redline for the d15b7 is 6800 so I am inclined to disagree with them. If it is a rev limiter, I have no idea why it's there or how to get rid of it.
I am 80% sure the ECU is the issue, as all of the symptoms I have listed seem to be normally caused by a faulty ECU. I just have no idea why a brand-new one tuned exactly for my car wouldn't even let it start. If you have any idea why or have experienced something similar to this and found a solution, please let me know. Even if you've only experienced one of the issues listed I would really appreciate anybody who has a solution or advice, thanks.
