I've been having high idle problems lately (1000 and above at times) and I'm pretty sure it's related to the idle microswitch that comes in contact with the throttle linkage.
When idling high, I'll depress the little roller and idle returns to normal. (750rpms in neutral; 500 or so in drive)
I've tried adjusting the throttle cable via the adjusting screw so that the linkage depresses the microswitch roller further in, but no luck. Pic attached shows the microswitch in the idle position -- does this look normal or should the roller be closer to the switch itself?
Here's a blurb from another post I dug up:
I had a similar promlem with unstable idle on my 300CE and the problem was the idle microswitch.
Make sure all the linkage and the switch are clean , mine was covered in oily dirt , then check that the microswitch clicks every time the gas pedal is up.
You may need to bend the switch arm very slightly to make it work every time
I can't quite decipher what the poster means when he says to make sure the microswitch "clicks" every time the gas pedal is up. The quote is courtesy of Larry Smith.
Any insight/advice/thoughts is appreciated as always
'91 300E, 213K miles