My 1986 190E 16V just spent the last two days at my friends Mercedes Shop with no solution on this weird idle problem. I have spent some time reading about similar problems on this and other boards and the typical answer is wait till it totally breaks or replace sensors until its gone.

The Problem: after a sustained run on a freeway or open road, anything over 5 minutes - the engine will idle high either at 1500 or 2000 RPM for about 30 seconds before finding its way back to 900-1000 area. Sometimes, but rarely the engine will rev up and down on its own after such a sustained run. -- Another symtom is after driving it for about 15 minutes or so - letting it fully warm up, if you park it and try to start it 5 minutes or so later, the engine will stall and act eratic for the first minute or so, almost like the computer does not know where it is. The stalling eventually goes away and after that it is fine - just the other problem listed above.

The Mechanic Diagnosis: he narrowed it down to one of three things
1) Air Flow Sensor (the one in the throttle body), 2) Throttle Position indicator, or 3) the CIS itself -

now the problem is each of these parts is expensive and not returnable, so I was wondering if anybody had experience with these problems? - I am sure they are pretty common with the 16 valve - after reading all the post on it.

Also - if possible, does anyone have any of these parts from an old wreck 16 valve, a 16 valve that is being used for racing and does not need these parts due to modification - or wherever that they would be willing to sell?

Thanks Ahead of Time
Pete

Pete,
The symptom I had with a bad throttle position sensor was noticable during gear change. With a warm engine, when changing gears the RPM's would fall very slowly from 4000 to 2500 RPM or so. A new TPS solved this.

I also have a problem similar to what you describe, although not exactly the same. When fully warmed, if the car is shut down and started after a short while it tends to die unless a very slight amount of throttle is applied to get the idle up. This only happens on warm days, say 80 degrees on up. I haven't had the time to track this down yet.

You may want to try the throttle position sensor (switch) first, as it is relatively inexpensive, about $25 I think and easy to replace yourself.

Btw, where are you located?

The most common cause is the air flow housing!! Benzmac had the same problem with his & it was already a replacement housing. YOU can bypass the throttle switch with a jumper wire across terminals 1 & 2, for testing!

i am not presuming to know more than MB Doc, however, in my experience and from several of the local 16v owners that i have spoken to, this is a common problem with this car. I myself have had this happen. It would appear that the root cause of the problem is the CIS system itself.

The Bosch CIS system is pretty good provided it is strictly the mechanical version. The KE system installed in the 16v is electronically controlled and as a result can be very difficult to set up properly. Two of the mb techs i deal with here are shop foremen in mb dealerships and both have owned 16vs. one still does and both of them say that this is normal behaviour.

one thing that seems to work in bringing the idle back to normal when it sticks is to lightly blip the throttle.

i hope this helps.

i have the same problem with my 86 190e-16. and i've taken it to so called mbz repair shops and nobody seems to be able to diagnose the cause.
my mbz has a diagnostic device, which some kind of a tool plugs into it and it will eventually give me a code which in turn tells me the part in my car that is failing.

What i want to know is if you guys carry this tool and for those of you who are technicians will it diagnose my problem?

TRY doing a search on air flow sensor housing. YES almost all 16V's do this & that is because the CIS computer goes into fixed operating mode whenever there is a fault. AT dealer we replaced almost all of these under warranty. THAT was over 10 years ago. THOSE replacement housings were special ones that BOSCH made with very fine adjustment for this problem. I have an internal memo on this subject!! I do have a 16V myself & so does Benzmac, so not blowing smoke! JUST trying to help!

so where would I go about obtaining one of these air flow housings,
or is that the one currently being sold as a replacement.

I have figured out, that with this limited production car, comes a lot of gremlins such as this one - I am just trying to make sure I know what is going on so I can get a base line (so to speak) and maybe remedy a few of the problems


thanks for the help