For search archives, let it be known: 107 body 117 Motor, Idle jumping up and down and car stalling at idle or throttle closed. The Tachometer showed wrong RPM and the fuel pump relay was clicking like mad. Replaced Fuel Pump Relay, idle speed control and Air Slide Valve but still had symptoms. Checked all ground wires. Borrowed a neighbor’s Ignition Control unit and it runs fine. I ordered today through Fast Lane.
Mystery solved. I saw lots of posts but few-said ICU. I don’t know how the Tach is connected to the ICU, but it must be.
Now I am on to the next projects.
’85 500SL (Euro)