91 2.0 irratic idle - Average 4 Door

I have just got myself a 190e 2.0 1991 on a 'H' plate, its got around 65,000 on it and is a real cracker.......apart from the fact she idles about 15-18,000 rpm whilst in park and neutral then drops to 1000ish when you put her in drive. Its pot luck as to wether or not she stalls or the idle fluctuates between 500 to 1800 rpm.
Sometimes she drives ok but always idles really roughly.
I have changed the dizzy cap and rota arm and was told the previous owner had the fuel distributer and fuel filter changed all to no avail. I have also tried a new idle control valve again to no avail.
I have since re fitted the original valve but was wondering which way round it went?? I dropped it putting it on and have tried it both ways round and the problem still persists, basically i am asking does the arrow point towards the bottom of the inlet manifold or the top??

I have limited funds to get the car going so was wondering if anyone had any ides of what to try or possible causes of my problem.....

Thanks in advance Jon.
91 2.0 irratic idle - Number_Cruncher
The arrow points in the irection of the airflow.

The first thing to check is that no previous meddler has over adjusted your throttle cable, or, even worse, reset the throttle closed position. There will be an electrical switch which will make contact at idle, and if it isn't making contact, your idle will not be being controlled.

Is the ABS light also on? (or, has the bulb been taken out?)

91 2.0 irratic idle - Roger Jones
You have a C-class W201, not an E-class W124.

N_C knows what he's talking about, but if you need to search for further help, here are all or most of the worthwhile MB forums. The big US ones have sections by model.



Edited by Roger Jones on 11/04/2009 at 13:30

91 2.0 irratic idle - Average 4 Door
throttle cable looks fine, little bit if play in it....not overly tight or slack. The electrical contact also looks fine, as you tighten the throttle cable it pops out and as you let it off it goes back in. ABS light is on when the car is being turned on and goes off as soon as it starts and ticks over, whilst the idle is too fast it stays off.
Just been out to it now, it started fine but went straight to approx 1700 rpm whilst in park, put it in drive it drops to around 1000. it only seems to be when it is hot the idle fluctuates like crazy....almost like its 'hunting'.
i would not know about the throttle closed position as i do not know how to check this, and further info ideas would be greatfully appreciated.
91 2.0 irratic idle - Number_Cruncher
It sounds like either the throttle plate is set too far open, or there's an air leak alling air to bypass the throttle.

There will be a method to set up the base throttle position - sorry, I don't know it off the top of my head.

It will be along the lines of;

- clean the throttle body and throttle plate
- slacken the throttle position switch adjustment
- fully slacken the throttle stop screw - also fully slacken the cable
- snap the throttle open, and allow it to shut with the spring (the plate should lock into the body)
- screw in the throttle stop screw until the throttle plate bumps free of the bore
- tighten another quarter of a turn, and lock the locknut
- reset the throttle position switch
- reset the throttle cable

It will be worth asking on either mbclub or mercedesclub.org to find the correct method.

If there is either too much throttle opening, or a major leak, the idle speed controller will not be able to compensate - it's only meant to control/compensate for small changes