High idle rpm on 1993 300SL

[valtchov]

Hello,

I have a 1993 300SL (W129, 104 engine), when started from cold the car idles at around 1100rpm. After driving and warming up, when the gear selector is returned from D to N or P the idle RPM goes to 1500 - 2000 and stays there even after briefly depressing the accelerator. Any ideas as to what might be going wrong will be greatly appreciated. I have checked the throttle linkages and at idle they seem to be in the correct position. Many thanks in advance

Valtcho

[Benzmac]

You need to check the throttle switch to be sure that the idle portion is working. Next, the idle control valve is in order to check.

If you don't know what I am talking about, take it to a tech. The idle systems are very complex for those who haven't the experience on diagnosis of Mercedes.

[valtchov]

Many thanks - will check those two items out this week. I have been reading up on the fuel injection system so I know exactly what you are referring to.

Regards

Valtcho

[chronodeco]

Benzmac - I have the exact same problem with my 92 300CE. I know this is an old post. Are there any other posts that go into some detail about how the check the trottle switch and the idle control valve. Thanks, Craig

[mcdill]

Valtcho,

Did you ever fix this problem? If so, what was wrong? Please let me know.


Thanks,

Matt

[chronodeco]

I took the lines off the trottle control vavle and sprayed carb cleaner in it and put clamps on the hoses after I put them back on. I also ran 2 bottle of techron in a 1/3 tank of gas. The problem went away in a day. Try the techron 1st. Craig