M50 erratic idle

[Dave M]

About a year ago on start-up, the M50 idle reved up to @ 3000 rpm, then back to 700, continuing this until turned off and re-started. While doing this dance, I noticed the ‘check engine’ light was on (the first time I’ve ever seen this). Recently, this has happened on a few occasionson start-up and even while on the highway (I notice check engine light, dis-engage clutch at 100km/h and watch the revs dance, give it some gas and it stops).

I did a search and found a discussion on M50 eratic idle (http://www.bimmer.info/forum/showthread.php?t=11882&highlight=M50+idle) which mentions the ICV and throttle switch.

Has anyone experienced this? It occurs infrequently and is not a major concern as of yet, but would like to gat a handle on it before driveability becomes an issue.

Over and out,

Dave M

[Interceptor]

About a year ago on start-up, the M50 idle reved up to @ 3000 rpm, then back to 700, continuing this until turned off and re-started. While doing this dance, I noticed the ‘check engine’ light was on (the first time I’ve ever seen this). Recently, this has happened on a few occasionson start-up and even while on the highway (I notice check engine light, dis-engage clutch at 100km/h and watch the revs dance, give it some gas and it stops).

I did a search and found a discussion on M50 eratic idle (http://www.bimmer.info/forum/showthread.php?t=11882&highlight=M50+idle) which mentions the ICV and throttle switch.

Has anyone experienced this? It occurs infrequently and is not a major concern as of yet, but would like to gat a handle on it before driveability becomes an issue.
Try cleaning the ICV and maybe changing the O2 sensor.

[Dave M]

I thought O2, but its less than 50,000km 'new' and did the same thing with the old one.

Hmmm?

Dave M

[Interceptor]

I thought O2, but its less than 50,000km 'new' and did the same thing with the old one.
Maybe you have a vacuum leak somewhere?

[632 Regal]

I would also agree the ICV needs some attention. Inspect all the hoses for vacuum leaks too. Did you do the stomp test too?

[Dave M]

Regarding the stomp test, I've never had a reason to try until now, but wasn't successful on my first 'few' attempts. I seem to recal someone saying that Canadian models, or models outside the US do not have this option. $hit.

I've been suspect of a vacuum leak before and tried the plastic over an open oil filler cap. It sucked, so thats good:) right??

Thanks guys, I'll investigate the ICV.

Dave M

[Kalevera]

Dave -- I've seen a few cars with the same symptoms (sometimes no CE light, though) and it's usually the ICV. Unlike others, I don't clean them -- solvents can destroy the seals, but since you've got nothing to lose, might as well try. You might still want to locate a known good unit, though.

Sometimes they'll just idle at 3000rpm or they'll fluctuate as yours has done. Have fun replacing it -- M50 is just about the most difficult to access of the engines built during that era IMHO....they made it a bit easier for the M52.

best, whit

[Kakaire]

Dave -- I've seen a few cars with the same symptoms (sometimes no CE light, though) and it's usually the ICV. Unlike others, I don't clean them -- solvents can destroy the seals, but since you've got nothing to lose, might as well try. You might still want to locate a known good unit, though.

Sometimes they'll just idle at 3000rpm or they'll fluctuate as yours has done. Have fun replacing it -- M50 is just about the most difficult to access of the engines built during that era IMHO....they made it a bit easier for the M52.

best, whit
Just done mine a week back (ICV). I had similar simptoms, hunting idle upon startup when cold and Stalling between 1000-1700 rpms. First did the AFM and stalling was fixed but baby was still idling eratically, finally changed the ICV and noticed a big difference, not more stalling no idle hunting, I know drive with a smile.