W124 Fast Idle - new MB owner needs help

[nsundby]

Hello to all from a MB newbie. I purchased my first Mercedes a couple of weeks ago and would really appreciate some guidance please. It's a 1993 E220 TE W124 with the M111 16V engine. It's done 170k miles.

The problem is the idle speed. It starts fine from cold and idles at about 900 rpm, but this rises to about 1400rpm when it's fully warmed up. In all other respects it runs like a dream.

Is this a case of replacing the idle control unit?

Thank you for any guidance you can provide.

Nick

 

[tom7035]

You could try the following, which would only take a few minutes and no cost. If it doesn't help then you haven't done any harm anyway, and in the meantime others with more expertise than I will undoubtedly come in to help you.

There's a black plastic-like cover about 5" x 3" on the side of the throttle body which uses 4 'security' torx screws to prevent 'unauthorised' access. (These screws have a pin in the centre so you will need the torx bits with the hole in the nose to undo them). Inside is a very lightly sprung (or weighted) electronically controlled lever 'gizmo' which on mine was sticking and affecting the tickover in all sorts of ways. A squirt in the innards with magic WD40 did the trick! This was around 6 months ago and no problem since.

Good luck.

 

[nsundby]

Many thanks for your good suggestion. Unfortunately, it didn't help in this case.

Any other suggestions would be gratefully received.

Nick Sundby

 

[pascal]

I think you may have a problem with the idle control valve.
You can remove it and clean with a degreaser for starters.

 

[Myros]

cheap brake fluid

Pickle it over night in a small jar filled with cheap brake fluid. Works wonders, as well as taking all the part numbers off. Write them down before you do it. and don't drip any on your bodywork. Rinse it out withe petrol when you're done.

 

[nsundby]

I took out the OVP relay fuse, which was intact, and replaced it back in the relay. Bingo! Car starts and runs perfectly. Idle speed problem solved.

Many thanks to all who posted suggestions - I'm really impressed by the people contributing to this forum.

For others encountering the same problem on a W124, the OVP relay is behind the battery, to the right of the ECU. It's about 3 inches high with a fuse on the top.

Thanks again

Nick Sundby

 

[smokey]

look on my answer in fast idle smokey see iff this helps
Geoff