High Idle On My 85 380sl
 

Just recently started having a high Idle after startup.Warm or cold engine,in the 1500 rpm range.Did this one time a few weeks ago but normal till today.Even after driving for a while,it stays high.Any Ideas where to start?

Thanks in advance

high idle
 

Check your overvoltage protection relay to see if it is ok. Also check your airslide valve to make sure that it is not sticking.

high idle
 

Thanks,
But what is the Airslide valve? where is it located?

Its also called the idle air control valve. Its located at the front of the engine and it has two hoses connected to it and 1 two prong electrical connection. Should be silver in color.

high idle
 

Thanks BENZTEK,
OK,I know where it is now.I will take it out and clean and check for operation.Where is that overvoltage protector located?Also if it turns out to be an Idle control unit,where is that located.I have the CD but it is vague on locations of parts.

All of the electrical is probably located under the dash on the passenger side. The OVP is to the outside and the idle controller in about the middle. It is a black plastic box about the size of a pack of cigs with double the width.

Usually the problem is cold solder joints in the controller reducing the power to the valve. The controller also seems to be burdoned quite often by sticking valves that then require full power to try and move. Unfortunately this results in the need for both devices in many cases.

If you pull the connetion to the idle valve and the speed goes up, you probably don't have an OVP problem. The OVP powers the controller and usually will be either/or not variable. If the system works at all the OVP as probably turned on.

high idle
 

Thanks,
Im getting 12v to the idle control valve,when I disconnect there is no difference in rpm,its still around 1800.

The valve is controlled on the ground side, not the voltage side. Place a momentary ground to the ground side (with the power hooked to the other. If the valve shuts and the engine stalls, look to that OVP and/or controller solder joints.

high idle
 

Thanks Steve,
Before I read your message I had taken 12v to the valve while engine off and I could hear the valve piston clicking.Should I still try to hook up when at Idle?
benzthr

I had a faulty control module and was able to repair it myself by resoldering the board. It isn't as bad as you'd think. It just takes patience and basic soldering knowledge.