I have the same issue. When I start up my car it sits at about 500 on cold mornings after I rev it sits back down at about 750-800. I tried adjusting the rack damp. pin, but If I loosen it at all my car shakes terribly without any noticeble higher rpm on a cold idle. I have a feeling it might be timing related and I am going back to the drawing board with my injection pump this weekend. Ill probably give the millivolt method a try again although the last time It took me several hours to only get partially imrpoved results in the running of the engine.

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1983 300SD White with Grey interior