My 1986 190E 16V just spent the last two days at my friends Mercedes Shop with no solution on this weird idle problem. I have spent some time reading about similar problems on this and other boards and the typical answer is wait till it totally breaks or replace sensors until its gone.
The Problem: after a sustained run on a freeway or open road, anything over 5 minutes - the engine will idle high either at 1500 or 2000 RPM for about 30 seconds before finding its way back to 900-1000 area. Sometimes, but rarely the engine will rev up and down on its own after such a sustained run. -- Another symtom is after driving it for about 15 minutes or so - letting it fully warm up, if you park it and try to start it 5 minutes or so later, the engine will stall and act eratic for the first minute or so, almost like the computer does not know where it is. The stalling eventually goes away and after that it is fine - just the other problem listed above.
The Mechanic Diagnosis: he narrowed it down to one of three things
1) Air Flow Sensor (the one in the throttle body), 2) Throttle Position indicator, or 3) the CIS itself -
now the problem is each of these parts is expensive and not returnable, so I was wondering if anybody had experience with these problems? - I am sure they are pretty common with the 16 valve - after reading all the post on it.
Also - if possible, does anyone have any of these parts from an old wreck 16 valve, a 16 valve that is being used for racing and does not need these parts due to modification - or wherever that they would be willing to sell?
Thanks Ahead of Time