500slc high idle
 

Gang, I was wondering if I could get help for some of my issues.
I have two cars that both suffer from high idle.

My 450SLC 5.0 and 500SLC. Both are suffering from high idle issues when warm.

In Drive, the idle is right around 1000rpm and in Neutral, it's right around 1600rpm. Any thoughts as to how I can adjust this?

That happened to my 500SL when my idle contol "module" or "valve":confused: crapped out. It defaulted to a higher rpm similar to yours.

I'm sure a more knowledgeable forum member will chime in.

my 500 SEC did the same when the throttle position switch was left unplugged when I reinstalled the engine.

It turned out that if the TPS failed open, the engine goes high idle as well.
I ended up finding this by shorting the tps harness where it connects at the fender, and the car dropped back down to 600-700 rpm.

Al, have you checked the auxiliary air valve? I checked mine by removing from the engine and heating it up on a pot of water in the kitchen to check that it was in fact moving (wife was not too amused!). Works basically like a thermostat - as the engine heats it up, the valve closes and less air passes thru it. I'm no expert, but maybe something to check...

Trevor