Idle and drivability issues

[eric16v]

Hey guys I've been lurking around the site for some years now and I have found it quite useful. A little background: 91 318is M42 engine mainly stock With a MarkD 91 oct chip and 700 bosch injectors.

so lately I have been having trouble with the car. It first started a couple months ago. I would be driving along and come to a stop and the car would begin to act as if it was going to stall. I would have to give it throttle around 1500 rpms or it would stall. If i didn't catch it in time it would die. Then start up right after. It seemed to act normal once I got it going and the revs are up like on the freeway. I would notice the check engine light come on for second but go away when I gave it gas. Then the symptoms would go away for a week or even two.

Lately though it has gotten worse. Now it will completely dies when coming to a stop. It will start right up though after it dies. When I go to take off it will bog down for a second or 2 then kind of buck and sputter until the revs get up to around 2k.

This time I was able to get some codes from it.
C9 lambda and also 29 air flow meter. (using a peak diagnosis tool)

I tried testing the AFM with my meter and the resistance seems to be moving steadily although I couldn't get any readings on pins 4 and 5 for the IAT sensor.

I checked for spark. It was there. The plugs (NGK BKR6EK) seemed to be carbon fouled (dry black) and the exhaust smells rich.
will perform a fuel pressure test.
Also have redone all the vac lines under the intake.
Just wondering if anyone has had these codes. Ive read up all over the forum and noticed many people with similar issues but not to many fixes.

Sorry for the long post and any input and help is appreciated!

[Tgoode318]

Your ICV is Bad, Try cleaning it with carb cleaner and an old tooth brush. Some times they can get so bad that you have to replace the whole unit, but usually the carb cleaner/toothbrush is enough to get the plunger mechanism unstuck (Which is what cause's it to act as a dead mans switch if you let off the gas) If you verify the icv to be working properly after cleaning it i would next look to your AFM and try swapping it with a known working one if possible.
-TG

[eric16v]

Did a fuel pressure test and I had 40 psi. I don't think it is a fuel issue.

Does anybody know what the IAT sensor does? It is that small wire inside of the AFM. I don't seem to be getting any readings for it when I ohm it out. What symptoms does a bad one make? I don't really have a good one available to me to use as a test.

Thanks again

[Tgoode318]

IAT = Intake Air temp,  it measures the incoming air temperature so that the engine can adjust fuel trim. When its cold out for instance the air is more dense so it requires more fuel.

[Jay]

Test the spark plug wires. Open the cover and feel every wire if it shocks you you know it is faulty.
I had the same issue but my cause was that the ECU was toasted.

[eric16v]

I have a COP kit on the car. I tested to see if spark was there. It was but seemed a little weak.
I also noticed that my battery was not holding a charge. I had it for 14 years!
Anyway I replaced it with a new one and have yet to had any of these problems since. (going on 3 weeks)
So far so good

[keflaman]

Thanks for updating us on the "repair". Hope it holds!