1987 W124 M103 300E
Engines rev to 5000 + RPM at starting, I then shut off the car.
After 2 to 5 attempts it runs fine. Make no differences warm or cold.
Afraid to damage engine.

1-Have replaced Idle air control valve The 2 rubber hoses to the valve. ( Cracks found in the vacuum hoses / Detected from vacuum smoke test.)

2- Replaced OVP relay Car is running much better.

Engines still revs high only at start up, Same Scenario as before mentioned. Need best course of action, Thank you.

OK, the high rev. could be from an erratic electrical signal from the potentiometer,first the EHA reading should be set, then the on off ratio, and
the readings from the potentiometer,the o2 sensor is another link in the system,it too must be in good shape, all of this can be found by looking up each in the search, I have just completed some of this myself and have several post you can get info from.Good luck and if I can help Let Me Know,JNT

Pop the hood. Look at the end of the throttle linkage, there is a small lever with a roller that makes contact with the end of the throttle linkage every time the throttle is closed. It may be bad.Tap the pedal when you start the car to see if the rev comes down.

WOW. 5000? And I thought that my 2000 was high.

I had the same issue on my M103 and it was this switch that was faulty.

I 'VE NOW CHANGED THE MICRO SWITCH @ THE END OF THE THROTTLE LINKAGE & CLEANED ALL PART OF THE LINKAGE•••• Still rev very high at start up. STILL NEED HELP .... Thanks for all the input so far. Stephen

Pop the linkage from the throttle body look to see if the spring is in good shape pulling the plate closed. if it still revs high look for vacuum leaks if all that checks out then start looking for problems in the electrical signals for the pot or EHA.JNT

I've Notice W/ The Air Filter Off / Myself Looking Over The Throttle Linkage & A Second Person In The Driver Seat Ready On My Command To Turn The Key To Start The Engine. First Key Position ••• Fuel Pump Starts
2nd Key Position Linkage Starts To Open Automatically With One Click Sound Coming From Behind The Firewall ( Possibly Fuel Relay Starting It's Job) Then A Second Click From The Fire Wall Immediately Closes The Throttle Linkage.

Now With All That Said.
I Tell The Person To Start The Car Normally,
Situation From Above Happens ••• I'm Looking At The Throttle Linkage ••• Engine Starts ••• But Linkage Keeps On Opening And Engine Starts To Rev High To 5000 Plus Rpms.
I Do This Several Times••• 2 Out Of Five Times The Engine Revs High & The Other Times The Car Runs Perfectly Normal. Mentioned In Previous Post Is The Part That I Have Changed. Could It Be A Relay ?

Still Need Help.
Thanks For All The Inputs So Far,
Stephen.

Have you recently checked/replaced your O2 sensor?

Second, check if your cruise control is engaged if you have one.

the spring that holds the throttle closed,[unless you press accel]must either be broken or disconnected.with aircleaner off try moving the throttle linkage by hand and see if it snaps back.if this car was a 93 and had a 104 engine then early electronic accel could be problem.

__________________
David S Poole
European Performance
Dallas, TX
4696880422

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
http://www.w108.org/gallery/albums/A...1159.thumb.jpg

I Have Not Check The O2 Sensor. This Only Happens At Start Up.

I Will Also Ck The Cruise Control.

What Trigger The Relay To Open The Throttle Linkage Then After 2 Seconds Shuts It Off , For This To Have The Proper Fuel & Air Mixture For Start Up. ?