High Idle
 

My 1991 560 SEC has just started to idle high. 900 rpms in gear and 1400 in park. Warm or cold it`s the same.

Thanks,
John

hello John, this is your lucky day!!!

Actaully, high idle is the most common problem on these cars. I would suggest that you get a couple of your favorite drinks and do a search with "high idle". It may take you 3 days to finish all the reading.

With what you read, you could start to diagnose your car one source at a time. Report back what you found in details and see if we could talk about.

I have been fighting the ghigh idle issue on my 1991 560 SEL for the past three months. It could be good for a coupel of days but most of the time it runs just like yours.

High Idle
 

I found the problem.

It was the small clear vaccum line attached to the PCV hose coming off the rear of the right side valve cover. Must have come off when I removed the air cleaner for cleaning.

John