Fast idle Question
 

I have a 1991 300E. It idles fast, but will come down to a normal idle speed when you goose the gas pedal and will then again go to a fast idle when you drive it. Then your able to kick it down again. I believe it is an adjustment in the mechanical linkage. Any suggestions on adjusting this linkage or any literatute on this subject. I've searched everywhere and can't seem to come up with an answer. Thanks

Had the same problem with my 2.6. Turned out that the throttle position switch was not sending the idle signal. The fix was to partially disassemble the throttle linkage (the ball and socket joints down low), clean, lubricate, and adjust. The TPS is located under the fuel distributor at the end of the throttle shaft. It has three leads - idle signal, WOT signal, and ground and has a pigtail with a connector in the harness channel that runs transversely across the top of the manifold, so it is easy to disconnect and check for continuity of the correct pair at WOT and idle.

Also check that the microswitch on the top of the manifold sends the proper idle signal.

Duke

Had a similar problem with our '91 190E. Turned out to be a broken plastic adjuster on the linkage end of the cable. It would hang up, preventing the throttle from returning to proper idle position. Replaced the cable and cleaned the linkage, and it returned properly and consistently after that.

Steve