w126 high idle
 

I know this has been posted about a lot but I'm stumped. I did a diagnosis based on the cd and determined the ICU was bad. So I replaced a few transistors tht were bad and it held the idle for a while but slowly over time high idle again. So I bought a used icu from my Benz part guy I go to and it worked for about 10-15 min and the idle went bad again. So this last time I checked all the diodes on the board, they seemed good, and replaced all electrolytik caps all ic chips and all xistors. Once again same problem. I'm stumped. I really doubt this prob is based on a faulty diode or cap tht I didn't replace but I suppose itds possible. Ideas?

You may be drawing in air somewhere.

How would I check for a leak?

I don't see mention of which W126 you have - there are many.

Use the advanced search feature under search then look for high idle in titles only - tech sections - many hits.

You might also search for fast idle

EGR valve might be blocked.

Its a 1985 500sel

once again high idle issues 84 500sel - Benzworld.org - Mercedes-Benz Discussion Forum


85 500sel high idle - Benzworld.org - Mercedes-Benz Discussion Forum