'83 380 SL 296k miles. starts fine, idle at 650. When the temp reaches about 85C the idle Sometimes jumps to either 1100 or 1400 rpm. Again sometimes the idle stays high for only about 1 min then is normal. At other times it stays high.

When idle is normal the voltage at the idle solenoid is 14.0v. When the idle is high the voltage is .2v. Recently replaced the temp switch. The idle controller and solenoid were replaced in 1994 (about 30k miles ago). Checked the idle speed according to the shop manual with the throttle position switch disconnected and temp switch by the oil filter disconnected. Tested OK.

I have attempted to test the output voltage of the idle controller but each time I turn the engine off the idle is OK on restart!

Fast idle is not affected by AC on or off. Car runs fine otherwise. All rubber vac parts and idle circuit parts were replaced in 1994.

?

Bill Dormandy
Dorvbell@compuserve.com

Idle Speed Control Modules have bad solder joints over time. I resoldered mine and it fixed the problem you describe. I could put my car in neutral and rev the engine once and that would bring the idle speed back down to normal every time. Seemed kind of silly sitting in traffic in a 380SE, reving the engine.

Voltage to the idle valve is supposed to be 4-6V at hot idle. 14V to hold 650 would indicate a bad valve and will probably fry the conrol unit. Or maybe something binding in the linkage is causing a high idle and the controller is trying to bring it down.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Hello,
After reading many posts and having the same high idle situation as most I am going to attempt the DIY fixes first. That is check for loose wires on the idle control module and then re-solder the connections as suggested by some. My question, is there any secret to removing the glove box in my 380 SL to get to it. The books and cd's I have tell where the module is but give no instructions to remove the glove box. Seems pretty basic I know, please indulge me.
Best Wishes,
John