It's just a two pole SWITCH (open or closed on each of the two circuits - NOT a potentiometer) to tell the ECU that the throttle is either at idle so it can manage idle speed or WOT so it will go into open loop and enrich the mixture. Obviously, if the ECU never gets the idle signal from the switch, the idle stabilization system will never take over idle speed control, and you end up with a high idle speed.

The idle side should read closed (zero ohms) at idle and infinity when the throttle moves off idle. The WOT side should read zero at WOT and infinity at less than WOT. Your problem sounds like what I experienced. The WOT circuit was fine - got continutiy between the proper pins, but when I closed the throttle the idle circuit portion of the switch (repeated this test several times) did not always show continuity. Snapping the throttle closed would usually give continuity - just as kicking the throttle would usually bring the idle speed down to the proper level when the problem started occurring.

The microswitch on the linkage can be checked in a similar manner by disconnecting the wires and manually exercising it and watching the meter swing between zero and infinity.

I think a good cleaning/adjusting/lubrication of your entire throttle linkage will solve the problem. Pay particular attention to cleaning the area around the throttle valve switch and the idle stop on the opposite side of the throttle valve shaft with a spray bottle of mineral spirits or Gumout or equivalent. Also make sure there is enough slack in the lower linkage to let the throttle shaft lever fully rest against the stop.

Based on my own experience and anecdotal evidence from others I think the throttle valve switch is the MOST COMMON CAUSE of high idle problems, but most advise to look at everything else, BUT the throttle valve switch. I don't think most even know it's there.

One other thing. According to the MB documentation that I have on the KE system the airflow potentiometer signal is ONLY used by the ECU to provide acceleration enrichment when the engine is cold - before it goes into closed loop operation. It has absolutely nothing to do with the idle speed control function. This is from the "Model Year 1984" manual that describes the new 190 and its various systems. There were some changes to the KE system in later years, but I don't think the airflow pot/idle system relationship was one of them.

Duke