1989 560sl idles fast. How to correct idle?

Asked by Mar 13, 2016 at 10:31 PM about the 1989 Mercedes-Benz 560-Class 560SL Convertible

Question type: General

Cold idle is fine, 750rpm operating temp idle 800-1299rpm. I suspect the idle control valve but my mechanic wants to replace the electronic module for $700.+. Any suggestions?

1 Answer

55

Typically when the idle control valve fails it will idle at a much higher RPM. You can try tapping on the valve and see if the RPM changes. Also, it is very common for this engine to have vacuum leaks. Finally, the idle position switch can fail and the idle will usually be in that range when hot.

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