Idle speed diagnostics - 1982 380SL

[300sdToronto]

I have a high idle when the engine is warm in my 82 380SL. Sits at about 1200 rpms in P or N.

I measured the voltage on the pins of the idle control valve (cylindrical device on the top, front of the engine) by sliding the connector back without disconnecting it, and saw a voltage of 3.35 to 3.5V. When I disconnected the electrical connector to the valve the RPMs immediately jumped up another 500 revs or so. When I slid the connector back on revs settled back down at 1200 within one or two seconds.

I assume this gives the idle control unit and the valve a clean bill of health and I should look at disconnecting the oil temp sensor next and see if that makes a difference?

A quick prod in the right direction would be appreciated - thanks.

[rockcrusher]

Have you looked for any vacume leaks???? This is the most common cause I have seen posted here. Try a search for high idle, should produce plenty of reading material for you. I also chased the high idle for a while, found some questionable connections, one hard plastic line from the warm up regulator (WUR) lower port to the switch over valve on the throttle valve housing cracked and broke when I was checking the lines. What a SOB to fix, and I just temp fixed it for now. Then I pulled the ICU out and looked at it and found a burnt board. Replaced it and Wala, nice smooth idle. Good Luck,

[rgp717]

Hi, I too am chasing high idle (and still no solution). However, with regards to your Idle Control Valve, I suggest further testing. My valve also yields 3.5V across the pins, but I'm convinced it is bad.

Remove the connector and put 12V across the pins momentarily (less than 5 seconds). It should make an audible clunk (at least this is what I read). I used a car battery with 2 leads, but I read some clever person used a 9V battery to perform the test.

In my case, no clunk ... no nothing. But I was getting 3.5V across the pins. My new(er) ICV makes a clunk with I put 12V across the pins.