1985 w126 500 sel high idle

[discoking]

So after a couple months of being spot on my 500 sel has the high idle problem. It happened twice in the last 2 weeks but each time after work and driving home it would be fine again. The last 2 days however have seen the high idle each and every time I start it up. It revs at 1300 in N or P and 1000 in D. It did used to idle perfectly at 550 in D and 850 in p

I've done a lot of searching and have done basic things like check the vacuum and throttle linkage but wondered if there were any things, like pulling connectors etc out that could help me pinpoint what it could be out of the usual suspects before I just go ahead and order idle control valve 1st and see if thats the culprit.

Mine is a pre face lift car without the passenger footwell relay.

 

[mattkh]

Love the picture.
The idle control valve can be easily cleaned with an overnight soak, bench tested and refitted.

 

[discoking]

Love the picture.
The idle control valve can be easily cleaned with an overnight soak, bench tested and refitted.

Thanks man.

I'd read you can give them a clean (with mixed results) but since I got this car to be my daily driver for the next 5+yrs I ordered a new one. However last night after work it all was normal again, sweet stable low revs. And again this morning. I'll get the new one and wait and see if high idle returns and if it does swap it straight out.

 

[discoking]

Solved!

Crazy at this sounds but it was the cruise control. I thought it wasn't working and it isn't, well not as it should. I'm on my usual journey into work and cruising at 40mph along the coast and gave the cruise stalk a go, multiple times in all directions but to what I thought was no avail. Anyways comes to next roundabout and slow down and notice it's high revving again. Pull away and get back up to speed and I just hit the cruise off and the revs dropped instantly to normal. Tried it again and engage cruise and the revs up, disengage and they fall to normal. It even does it while staionary in P/N and D. Will cancel the ICV tomorrow morning.

 

[mattkh]

Well done.