Bouncing idle while rolling

[sludge1300]

My idle has been bouncing up and down when my car is rolling forward. Seems a bit strange as it won't do it when it's stopped. Otherwise the engine seems to be running well.

So far I've checked for vacuum leaks visually and sprayed lots of starting fluid everywhere. Haven't found any leaks. I also cleaned the MAF.

Engine is an OBD1 M52.

Any ideas?

Thanks

[berlow94]

Auto or manual?

[sludge1300]

Auto or manual?

manual.

[Fusion]

Happens to me too. No idea why. I pop into neutral and coast to a red light and the revs bounce a couple times from 500-800 or so.

[butters]

some light reading... http://forums.bimmerforums.com/forum...oaching-lights

I've adjusted my technique to minimize the effect, basically you can't simply drop into neutral from elevated rpm. let us know if you find the fix.

[berlow94]

Chip? Lightweight flywheel?

[sludge1300]

some light reading... http://forums.bimmerforums.com/forum...oaching-lights

I've adjusted my technique to minimize the effect, basically you can't simply drop into neutral from elevated rpm. let us know if you find the fix.

Great link. Thanks. Plenty of things in there I can try.

Chip? Lightweight flywheel?

TRM chip. Stock flywheel.

Auto or manual?

Oops, I forgot actually that my car's a manual swap. Of course I'm running that one red DME that deletes EWS or whatever. Can't remember the deal for some reason.

[justin_l_]

I know it's a differen car, but I had to adjust my Coast fc setting. Maybe it is an issue with the tune? I don't know if they can adjust the coasting fuel cut on our ecu's or not.

[ClausE30]

This happens to me too, sometimes it stalls while rolling to a stop in neutral

[maclogos]

I always thought it was due to the fact that you are in motion the airflow can cause this. My m50 does this too and i have had many mechanics tell me its normal when the car is rolling in neutral. Maybe they just say that since they dont wanna fix it lol. Other than that my car runs well. Idle is perfect at a full stop.

[nando]

it's the idle control. it's not catching the engine as the RPMs drop too fast - could be settings, could be the ICV being gummed up, etc. vac leaks will make it worse, so will a light flywheel.

[328ijunkie]

^+1 not normal for the most part.

[sludge1300]

Swapped the DME: no change. Cleaned the ICV: decreased the amplitude of the idle bounce, but didn't fix it.
Unfortunately I don't have another chip that I could try

[mitchlevy7]

this happened when I replaced my ICV. had to disconnect the battery and let the ecu reset and relearn the ICV and it worked fine afterwards.

[bzboardz]

this happened to me, ended up being one of the 3 wires to the TPS was corroded and not making contact. good luck!