85 380sl stalls when engine is warmed up

[webwurks]

My 1985 380sl starts up easily, idles perfectly, acceleration is very responsive until the car engine has warmed up. Once warmed up the car idle drops so low that the car stalls.
If I disconnect the idle control unit the car does not do this. It will continue to idle - allbeit a little high - after the engine warms up.
I've tested the voltage to the ICU and it consistently is 12v+ even after warm up. I have read that it should be 4-6volts once warmed up.

I have been working on this Mercedes for around 4 months as I have had time. I have replaced or rebuilt all of the fuel components from the tank to and including the injectors. The car sat for 14 years before I got.

Any suggestions on what to test or why the ICU is getting more voltage than it is supposed to after warm up? I replaced the Idle relay switch in the dash with no change in the issue.

Any suggestions will be greatly appreciated. I'm so close to taking it for a long drive up the coast.

[Sugar Bear]

Similar symptoms on an '81 380 SEL drove me crazy, really seemed fuel related...corroded ignition coil tower. New coil and wire solved the issue.

[Skid Row Joe]

Vapor Lock.

[agillot1947@gmail.com]

Originally Posted by webwurks

My 1985 380sl starts up easily, idles perfectly, acceleration is very responsive until the car engine has warmed up. Once warmed up the car idle drops so low that the car stalls.
If I disconnect the idle control unit the car does not do this. It will continue to idle - allbeit a little high - after the engine warms up.
I've tested the voltage to the ICU and it consistently is 12v+ even after warm up. I have read that it should be 4-6volts once warmed up.

I have been working on this Mercedes for around 4 months as I have had time. I have replaced or rebuilt all of the fuel components from the tank to and including the injectors. The car sat for 14 years before I got.

Any suggestions on what to test or why the ICU is getting more voltage than it is supposed to after warm up? I replaced the Idle relay switch in the dash with no change in the issue.

Any suggestions will be greatly appreciated. I'm so close to taking it for a long drive up the coast.

When you unplug the air idle valve , on a clean / free valve , the idle jumps fast , when you plug it back in it goes back to correct idle fast . When the valve become gummy , when you plug it back in it will stick and shut off . remove valve use carb cleaner , work it on the battery to energize it , only quick burst , dont use 12v too long , the valve noise will change , now the plunger in it will move freely .