RPM surge when starting hot
 

I noticed that sometimes, when the engine is fully warmed up, if I start it, the rpm surge to 1,500rpm or so, then drop really low to about 500, and then stabilize at 750rpm idle.

Is there something wrong?

What YEAR & model car?

1994 E220 Coupe
M111 2.2L engine.
100,000km/62,000m on it
Always garaged and maintained

Anybody?

Pull any codes and that will give you a better idea. I think yours will be compatible with the home made code reader on this site.

Things that spring to mind could be ETA or MAF.

Codes will help.

The CEL isn't on, could there still be codes?
Also, other than that, the engine runs fine.
The only complaint I have is that it's a bit noisy, and I can feel vibration from it but the mounts have sagged and I am thinking it may have an exhaust leak

Yes you can have codes without a check engine light. I've been in this situation.

Hell, I'm pretty sure my 1996 doesn't even have a check engine light. My previous MB's haven't either. Possibly something to do with the market they were built for - not sure.

I believe the Check engine light only triggers for emissions codes - can someone confirm ?

Ok, next time I take the car out I will take it to my mechanic to do a code check.


I know my other car has a dual length intake manifold, and the CEL didn't come on, though a code check brought up an error in the intake manifold + something with the alternator