89 300ce runs great w/ICV disconnected

108k miles and idling rough stalling and sometimes idling at 1200 rpm + and missing. I checked for vacuum leaks and found none. Disconnected the idle control and the car runs great and idles smoothly at 800 RPM. It does idle very low (around 550 RPM) until warm though. Is it OK to leave the ICV disconnected. I am still not sure that it is the root problem. Thanks for your help.

[lkchris]

Idle control valve bypasses throttle to provide more air as needed, especially when engine is cold and receiving extra fuel ("choke").

Perhaps removing this extra air makes your other vacuum leaks not so problematic?

[89-300ce]

Originally Posted by amhobby

108k miles and idling rough stalling and sometimes idling at 1200 rpm + and missing. I checked for vacuum leaks and found none. Disconnected the idle control and the car runs great and idles smoothly at 800 RPM. It does idle very low (around 550 RPM) until warm though. Is it OK to leave the ICV disconnected. I am still not sure that it is the root problem. Thanks for your help.

Same car, same miles, same boat. The 1200rpm idle is the throttle valve switch not closing properly. Do a search. Easy fix. The low, inconsistant idle I'm not sure. Mine sometimes idles as expected and sometimes low. I suspect a weak ICV. Maybe someone can clarify but I don't think that idle rpm is in a feed-back loop so it's just a mapped signal. Also suspect the OVP relay since low power output there could conceivably affect ICV operation. I do have a new OVP though, so who knows?

Jorg