Runaway idle while moving

[redandgearhead]

Driving home yesterday, my '94 525i developed a weird idle problem. If the car is moving, the engine speed won't go much below 2500 RPM and sometimes has high as 4500 RPM. I can drive at 60 - 65 MPH with the car at around 3000 RPM with my foot off the throttle (and the cruise control off), then push in the clutch and the RPM won't change much, might increase some.

If the throttle was physically stuck by something, I would think the RPM would zoom way up if the clutch pedal was pushed in. I'm thinking this is somehow commanded by the computer.

I also have a '89 325i that had a zooming throttle problem that was traced to a corroded connector sitting under the intake manifold leading up to the throttle body. I'm thinking maybe this is something similar

The aggrevating thing is if I stop, by the time I can jump out of the car and try to lift the hood to see if the throttle is stuck open, the idle goes back to normal.

The first step in my plan is to look for manifold leaks.

Anyone else have the same problem?

Thanks

Joe B.

[Blitzkrieg Bob]

my X wife had this problem.... turned out to be the floor mat riding up against the peddal.

Does the idle surge? if so.. check the hose to the ICV and the valve cover vent hoses too. when they leak the idle goes high and sometimes starts to surge.

[repenttokyo]

I had / still have the exact same problem in my car.

It is most likely the ICV. I cleaned mine and it helped a lot, but it needs to replaced to make the problem go away completely.

Other things to look for are the rubber elbows between the MAF and the throttle - mine had a huge tear in it that could not be seen from above. very cheap to replace, and it will keep air getting in while you are moving.

[Dave M]

I store my 525 (M50) in the winter and upon resurrecting it every spring, it will do exactly that (not as high rpm wise) and hunt for idle ONLY when the car is moving. Even at 10km/h it will hunt for idle and as soon as I come to a complete stop, it finds 700 and stays there. As this lasts a few weeks, I don't care, but wouldn't mind knowing.

Sorry I wasn't any help, just commiserating with you.

Dave