Here is my problem, some things ive experimented with, etc.
Car is a '91 318is (obviously
).
When the car is cold, its fine. After driving for 3-4 minutes, problems start, and continue until you let the car get cold again, like overnight. Problem is that when you let the clutch out and go from a stop, the car lags and sounds awful. Idle is a little rough (900-600), but when the revs drop at all from 800, the car sounds like its misfiring a bit. Then say I rev it up to 1400 and let the clutch out, then move the accelerator down a bit more (say to 1/2 - 3/4 of its max) to pick up speed, it doesn't really die when you let the clutch out, but when it should start to accelerate, it does so very slowly, and you can hear the engine stuggle (sounds sort of like misfiring, or a bad A/F ratio?). At some point, keeping the accelerator down at the same point, it will suddenly react the way it should - with the revs jumping up. Sometimes it gets itself together near the end of 1st, sometimes between the shift to second, and sometimes at the start of second. After it recovers and sounds and acts fine, it will remain fine until the revs drop down below 2000 for a few seconds, then I will have the same symptoms again.
Im not much of a mechanic myself, so I haven't checked too much myself. First mechanic looked things over, didn't find much except that my ignition coils were f*cked, so got that fixed, though it didn't solve my problem (and I didn't think it would). Then decided to try a fuel system clean from Mr. Lube. Ended up smoking up the joint, so that was a good thing (or a bad thing, depending on your point of view), and the car ran pretty solid after that, probably 85% better than before, so that was good. But my gas was pretty low, and when I filled up 3 days later, the car started acting like sh*t again.
I checked to make sure I had no obstructions in airflow, which I didn't, and changed the ECU (cause that takes 5 minutes) with a spare I have. The car runs worse with the spare - Im guessing this is because the spare has a stock chip, my standard has an aftermarket (TMS I think) chip - but what would the difference in chips change in mapping to make the stock one worse?
Ive watched my fuel efficiency, it hasn't noticeably varied (Ive driven a bit more highway, so I went a bit further on my last tank).
Ideas? Things to check? Anything else I should try while driving to try to isolate the problem?
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