surging idle/tps or icv opinions?

[Tim Hancock]

I am experiencing a surging idle and I have a TPS code in my memory (1992 325i). When the car is started and driven after sitting out in the cold with a cold engine after inital high idle thru warmup it surges at stoplights from 1000-1800 rpm it will CONTINUE this until you park it.

Funny thing is, if left sitting at a gas station or whatever, when restarted the idle will be normal (about 600-700 rpm) and will REMAIN good until parked for a few hours and allowed to cool down. The problem is going away due to heat soaking in the engine compartment when the car is at rest.

I could just dump $80 bucks on a new TPS but I am not convinced
due to the intermittant nature of this problem. After running the car awhile and shutting it down then restarting to "fix" my problem, I shut it down and restarted with the TPS disconnected and it did not surge (but did idle at 800 instead of the normal 650). This makes me think that it might be the ICV.

Any more troubleshooting suggestions?

[Jeron]

The TPS should be easy to test. On my 97, the test was simply to make sure there was a linear change in resistance through its range of motion, with no dropouts of course.

I had a bad ICV but the problem went away at the end of the cold start loop when the secondary air pump went off. After I cleaned it it got worse but replacing it fixed the problem.

Maybe the heatsoaking fix you are having is actually that the ICV stops sticking once it gets warm. I would remove and clean the ICV. If the problem changes after cleaning the ICV then replace it.

The electrical test for the ICV is also a resistance test across each pair of the 3 connections but the Bentley manual had the wrong ohms listed for my model.

Here's the thread where I listed my ICV experience:
Rough idle at startup

[Tim Hancock]

Thanks Jeron, the problem went away Friday and has not reoccurred since. I will try to clean the ICV if starts acting up again.