My '92 190E 2.3 will only idle if I disconnect the throttle micro-switch. I then idles ~900-1000 RPM. I have replaced the IAC, fuel pressure regulator, fuel filter, OVP. I put on a salvage-yard MAF with no change.

Occassionaly, it will start idling much higher than the 900-1000 RPM stated above. When this happens, I reconnect the micro-switch and for a few hours, it runs absolutely perfect. Also occassionally, it won't run at all. It seems that something is stuck.

I have recently re-worked the AC with a rebuilt compressor and R134 (if this has any bearing on the problem).

Any help is appreciated. Because of this unpredictable intermittent behavior, I cannot rely on the car at all.