'87 325e - Idle Starts to Hunt Once Hot - Good When Cold

[NJGreenBudd]

Hey R3V!

My 1987 325e has had a rough winter, the idle has been giving me trouble since fall and while I have made good progress it's still not right.

First thing was it would die right after startup, found the air intake boot had a HUGE tear in it on the bottom side. Fixed that and it now starts and runs no problem. Starts and idles solid around 1,000rpms with no significant trouble.

The current problem surfaces once the engine warms up, the idle will start to creep slightly higher and higher and will eventually start to hunt or rev up and down between say 800 and 1,500rpms. It drives okay and will stay running but this hunting idle is very bothersome at stop lights.

I have cleaned and tested the idle control valve and checked for any leaks but haven't found anything that seems to make a difference. Is there something in particular I should be looking at for hot idle hunting?

Thanks a ton, I greatly appreciate any help in resolving this problem.

Have a good one guys,
NJGB

[Kershaw]

how is your o2 sensor?

during the first 5 minutes of operation, they are essentially not used. after the car warms up a bit, they are. and if its bad, it'll affect everything. what you describe are the exact symptoms i had. a 1990 ford mustang 5.0 o2 sensor ($40) fixed the issue immediately. but a lot of things can cause those symptoms.

is the idle the only thing wrong?

[NJGreenBudd]

Thanks for the response. The O2 sensor(s) must be original, condition unknown. I can't remember if there are one or two sensors?

Let's just say idle is the only thing wrong that affects drivability, lol. I mean it starts and runs fine, drives good but the idle hunts once the engine is hot.

What else could be the culprit, any specifics on what to check, measure, clean, etc... would be greatly appreciated.

Thanks,
NJGB

[zshopa]

check your ICV

[NJGreenBudd]

I have cleaned and tested the idle control valve and checked for any leaks but haven't found anything that seems to make a difference. Is there something in particular I should be looking at for hot idle hunting?

In case you did not read the original posting.

Thanks,
NJGB