cold running problem

[Drake]

I've done alot of searching and tried a few things to no avail.

Car:1988 325is, no engine mods

When the car is cold the following occur:
1)Car idles low...around 450-500 rpm. Not a smooth idle, slightly rough.
2)Hesitates for a split second when I touch the gas
3)When I rev the engine it falls back below the idle point before returning to normal. i.e. I'll rev to 2000 rpm then lift off and the revs fall to like 300 (almost stalling) before returning to normal.

Here's what I've tried, suspecting it is running rich:
Changed Air Filter. Cleaned ICV (with electrical cleaner).

The car runs fine once warm (past about 1/4 temp).
The odd part is when I unplug the battery (resetting the ECU), the problems are then gone for about the next 3-5 hours of driving.

[Drake]

Did a measurement on the Coolant Temp Sensor and Switch. Things seem fine, even though I can't seem to find continuity to ground on the Coolant Temp Switch (when warm) as the Bentley suggests.

[kowalski]

check the icv to see if its actualy functional, where abouts in BC do you live cause iv got a spare one you can test with.

[Drake]

^^^

[kowalski]

huh?

[Drake]

Someone's gotta have an idea. What's stumping me is the fact that resetting the ECU makes it go away for a few hours.

[Drake]

Seems to be getting worse as time goes on. Working on it tomorrow. Anyone have suggestions?

[Drake]

Update

I've replaced the ICV and used propane to search for an intake leak. The problem is still there.

Once again, Problem (only when cold):
1)Hesitates when you hit the throttle,
2)After you blip the throttle the revs drop down below 500
3)Generally low/stumbly idle

My next idea is to find a cheap 173 ecu and see if that helps, as I know the 153 isn't the greatest. If anyone's got one they'll let go cheap let me know.

The engine's seems to be running well, did the plugs about a week ago and the old ones were great condition.

[Drake]

I should add that when I disconnect the ICV the symptom of the revs dropping below 500 goes away(although it still hesitates a bit)

[royalflush313]

I should add that when I disconnect the ICV the symptom of the revs dropping below 500 goes away(although it still hesitates a bit)

did you buy it used or new? There's always a possibility that the ICV is faulty, so maybe you should ask one of the 325 guys on bimmerclassics if they will let you swap the ICVs for a bit.

Is the problem ONLY when the engine is cold, and the problem goes away when for good when it's warmed up?

If so, would that show that the ICV is NOT the problem?

[mcgrath]

I have the exact same symptoms with my engine (84 325e 021 ecu) so far I have replaced all Coolant sensors, and the AFM. Everything else is functioning properly that I have tested. I think that it is either my TPS or the ECU is crap.

I put a chip in my ecu a few days ago. didn't help the running rich cold but gave a nice boost in performance when it's warmed up, so maybe it's the TPS. everything else is new.

[Drake]

There's a few guys that live near me with 325s that I'll try to hassle to let me use their ICV's for a bit.

Mcgrath, let me know if you find a solution, I'll do the same. Diff engine and whatever but may be same problem.

[nando]

test the throttle body switch. it affects your idle, my car idles at about 500rpm with it disconnected.