idle studder problem

[bimmerboy08]

Hey everyone I'm new to this forum but regularly post on a different e30 forum. I have a problem which I am having a lot of trouble solving. My car is idling terribly, below is a video:



this is only at idle, also in rare cases the car does something similar to a very gentle misfire when moving at low rpm, say like 35 in 4th gear. Other than that the car runs perfect. Here is what I've done to try and solve it:

All new ignition components
Searched for vacuum leaks
Compression test
New ICV
New MAF
Tried swapping out the ECU
New O2 sensor

The car is boosted and runs 8psi, and is also not exhibiting any signs of boost leaks. It uses a unichips piggyback ecu for fuel management, and was tuned by JE imports in Baltimore, MD. In the video you can see the MPG vacuum gauge snapping to the left, but the boost/vacuum gauge does not do the same thing.

Thanks for reading, any help would be greatly appreciated

[bimmerboy08]

Hey its all fixed, posting the solution so it may help someone in the future. It was the aftermarket fuel pressure regulator which was malfunctioning. It was dumping too much fuel into the engine at idle.

Also it looks like i posted in the wrong section. My bad.

[Wiglaf]

the idle on my 325e is messed up.. it's fine cold but once it warms up it'll climb up to 2k, then start bouncing from 1k to 2k then fall down again. people at stoplights think i'm trying to race them or something, it just keeps revving.
I checked the coolant sensors and throttle switch then called it quits, i pinched the ICV line with two pieces of plywood and some drywall screws. Tightened until it held at 800 or so rpms.

[DivineStyler]

Hey its all fixed, posting the solution so it may help someone in the future. It was the aftermarket fuel pressure regulator which was malfunctioning. It was dumping too much fuel into the engine at idle.

Also it looks like i posted in the wrong section. My bad.

Awesome... Thanks for posting the vid... My car is doing the exact same thing... wonder if it's the same cause on my vehicle...

[bimmerboy08]

Another thing to check if you have this problem is your crank position sensor, and the wire that is attached to it. If that wire becomes stripped and it grounds out it will cause this symptom as well.