I have been having idle problems with my 1991 500sl for several years now. I found quite a few threads with similar problems and I have managed to fix some of the issues but I still can't get a consistent 650 RPM idle. A smoke test revealed leaks in the rubber vacuum hoses under the air filters. I replaced all of them. The smoke test also showed that there might be a vacuum leak in the intake manifold gasket. I have removed the ICV and soaked it in thinner for 24 hours. I then tested the ICV by unplugging it while the engine was running and the idle shot up and then back down when I plugged it back in. I measured the voltage on the ICV and it never went above 4 volts. Does anyone have any ideas

 

Check out YOUTUBE videos lots of information on there .I thought it was the potentiometer but after looking on there i now dont think its that at all .But most interesting . Come back to you later .

 

Canns you watch the vidio on youtube ,go to the tube put in the box ------------ ---- -- Mercedes 500sl idle control valve problem shown good and bad valves .Did you say you had cleaned it out .Just remove the electric plug from the icv , before you start then see if you have stable idle with the air control valve conection removed or disconected ..

 

check around the injectors for vacuum leaks and did you check the throttle linkages to make sure they aren't hanging up?

 

I have watched a lot of videos but none have the same issues. Do you have a specific one in mind?

 

A smoke test revealed leaks in rubber hoses under the air filters but none in the injectors. The linkages seem to move freely but I could lubricate them. Any suggestions on what lubricant to use?

 

zoom gp oil MO98. that idle issue can be a real pain. you seem to have covered all the basics. problem with codes is that they are so generally vague. I had a problem with the idle, it would surge up and down from time to time. My issue after replacing most everthing else was the EHA electro-hydraulic actuator attached at the fuel distributor.

 

Cannes did you put in this ---- MERCEDES 500SL IDLE CONTROL VALVE PROBLEM SHOW GOOD AND BAD VALVE... did you put this in ? I saw it and its like your problem ..