E30 2.7 Idle issues.

[325Rudy]

Hey everyone, Ive had my 87 325 for a while now and lately the idle has gotten pretty ridiculous. Upon starting it revs to 2k rpm and stays there for about 15 seconds, then fluctuates between abut 800 and 2200 rpm. TPS is good, tried cleaning and changing ICV and the problem stays the same with either valve i tried. No vacuum leaks that i can find. Im at a loss as to what I should do so any help would be greatly appreciated.

[ROLLingKING]

deep creep?

[jlevie]

The only way to be sure that there aren't any intake leaks is to have a smoke test run on the intake. Until that is done, there i no point in considering the other possibilities.

[Myster-E]

If you have to use a smoke test to find a vacuum leak, you literally don't know how to work on cars. A can of brake cleaner or carb cleaner will work fine.

[325Rudy]

Im going to try the brake clean method tomorrow once im home again. I really need this to get fixed soon.

[325Rudy]

Alright no discernible vacuum leaks detected. I let it sit idling like crazy for a while and eventually it randomly evened out. i took it out for a rip around the block a few times and now its doing it again but not as bad. when i remove the oil filler cap it seems to even out. if i put the cap back on the idle surges again.

[jlevie]

If you have to use a smoke test to find a vacuum leak, you literally don't know how to work on cars. A can of brake cleaner or carb cleaner will work fine.

Carb cleaner works pretty well on sizeable leaks close to the head. It doesn't work well on small leaks and not at all on some of the leak locations. Plus it will only work if you get the fluid directly on the leak. A smoke test works regardless of the size of the leak or where it is. If a pro has a smoke machine, you'll not see him or her look for leaks with carb cleaner or similar for exactly those reasons.

[Myster-E]

Carb cleaner works pretty well on sizeable leaks close to the head. It doesn't work well on small leaks and not at all on some of the leak locations. Plus it will only work if you get the fluid directly on the leak. A smoke test works regardless of the size of the leak or where it is. If a pro has a smoke machine, you'll not see him or her look for leaks with carb cleaner or similar for exactly those reasons.

Congratulations

[kwill22]

Any progress?

[325Rudy]

Not really, the idle seemed to even out a little when i removed the oil filler cap, so i pulled the valve cover to clean out as much of the PVC/oil separator under there that i could. Didnt do anything. Im gonna try to test the ICM and MAF today. if its not either one of those im totally lost.

[kwill22]

Yea I hear ya. I'm in the same boat as you. Same car also.

[325Rudy]

Im currently borrowing a van to drive around until i fix this one. After its fixed im fairly certain shes getting sold.

[325Rudy]

ok so it seems the ICM is working because the ICV is fluttering and humming in there. The barn door has no binding in its movement. Im at a total loss as to what the problem is, anyone have any ideas?

[jlevie]

Rule out intake leaks with a smoke test, then check to see if the rail has normal pressure and make sure that the cold start valve isn't leaking once the engine is at normal temperature. Make darn sure that the idle switch in the TPS goes to short circuit when the throttle arm is 0.030-0.060" off the idle stop screw. Hearing the TPS click isn't proof that the switch actually works. If the O2 sensor has 100k on it, it has reached the end of it's useful life and needs to be replaced. If the problem persists, try a different ICM.

I really suspect intake leaks or a fuel system problem as the engine should have run very rough or even died when you removed to oil fill cap.

[slammin.e28]