IDLE issues, (bouncing) - '94 325i E36 M50

[HoyHoy]

Currently i am trying to diagnose an idling problem, and it is throwing me for a loop, i am hoping someone here has had a similar problem and could point me in the right direction for a solution.

Occasionally, my idle bounces from ~500 rpm --> ~1100 rpm; sometimes it even sounds like it might stall, but never does. It seems the worst at the first few stops i make after the engine is warm, and occasionally while the engine is still warming up but never or less pronounced when the car is cold. The issue seems much worse when high amperage electronics are on, (heater blower, rear defogger). This may be why it was less noticable until the temperature changed here.

I have replaced the MAF sensor, and the o2 sensor already. A mechanic suggested I try cleaning the ICV, which I did. Removing it, filling it with solvent, shaking it. repeating that a few times it seems the ICV is mechanically OK, but possibly not electronically. I have also checked the obvious vacuum leaks, such as the intake boot before the throttle body, throttle body gasket, and hoses from the boot to the ICV, as well as hoses from the CV breather connector... I'm stumped, anyone have any ideas or suggestions??

Sorry for the long post, I wanted to be as detailed as possible. Thanks in advance!
~Mike

[E36 Phantom]

Hey, welcome to the 'Fest, and a BIG thanks for the detailed post! :)

On a lot of the accordian type hoses, little cracks can come up that you don't notice easily. Sounds like you're pretty detailed, but it still might be worth a shot. Another think I'll go out on a limb on, if the problem is amplified when more accessories are on, and it only happens at idle, is perhaps your electrical system is weak and not providing enough power to the fuel pump. I doubt that's the problem, but it sounds plausible to me (maybe?).

Also, the best idea, since you have an OBDI car, you can pull codes yourself. There is a pedal trick that will blink the codes for you. Search a bit and it should come up. Good lcuk, and sorry about the problem. :(

[HoyHoy]

what is this pedal trick to pull the codes? do you have a link to a thread somewhere? nice lookin car btw, which headlights are those? i've been thinking about swapping mine out

[vwvannut]

I have a similar problem, when i apply the brakes to a stop i get a bounding idle for a few seconds and then it is fine, I've inspected all the hoses and cleaned the ICV as well, but i can't figure it out.

[E36 Phantom]

Pedal trick info:
http://www.bimmerzone.com/fcodes.htm

Thanks for the compliments - the lights are Depo Gen IV Euro projectors. I got them from Umnitza.com. I'm not happy with them, if I had it to do again I think I'd pop the extra couple hundred to get ZKW brand for better quality. But these were pretty cheap, so whatever. About 450 total, that also bought me the 2 front corners for 40 each, and (unknown to me at the time) piss-poor bulbs for another 50. Not a bad price at all, all things considered.

[HoyHoy]

so i figured out the problem... and i feel stupid for overlooking the obvious... as the engine paint deteriorated and flaked off, it broke the seal between the engine and the oil filler cap. sounds crazy but i literally pulled the small vacuum hose from the intake manifold that comes out of the CV breather connector. I was smoking a cigarette and started blowing smoke through it. smoke poured out from the oil filler cap. I scraped off the remaining paint in that area and used a super high grit emory paper to smooth it out. got a new oil filler cap, and the problem is gone. so simple i put about 20 hours of hose inspection and diagnostics in before i figured it out. i guess this is why shops have the fancy UV smoke machines... would have figured it out in seconds with one of those, instead of hours.
::sigh::

[E36 Phantom]

Naturally, its always one of those simple things we overlook...

[HoyHoy]

yea hope its something that simple for vwvannut above... he said he's having the same issue... hopefully he smokes cigs too and doesn't mind oil on his lips :-)

[eurokevin]

haha, i thought i was the only one with that idle problem. thanks for the info, i'll try that, but i gotta tear in my throttle body boot to fix first.