Hello again,

Thanks for all the comments and suggestions.

To update this thread, I have now got the car to a point where in Nuetral or Park it idles great. Around 550~600. I believe thats close to the spec [600~700 rpm].

However, when Drive or Reverse is selected the idle drops slowly to around 500 rpm. Then a bit lower and then starts to shake slightly.

This car is my wifes and she has put around 150 k miles on it. It never had engine vibrations before, sometimes slightly but would always go away. She is a bit nervous driving with it now the way it is.

To summarize items replaced so far were 1] EHA valve, 2] O2 sensor, 3] Fuel injectors, 4] Spark plugs[ Bosch 9DCO], CIS temp sender. These were all replaced based on analasis of the problem and the high mileage on the specific items. In excess of 100K miles.

Items replaced before this, [approx 100K miles ago ]were the Idle control valve, Fuel pump Relay, OVP relay, Idle position micro switch, plugs, points, HT wires and rotor.
This was to solve a stalling problem which worked.

I would love to squeeze anothe 50~100 rpm out of the CIS. This would solve my problem now.

I have some questions for "Andengines".............

Please bear with me on the Tech Lingo talk you have used, I'm not a mechanic!
The meter you talk of that has "duty cycle" is this a Multimeter? I have at my disposal a analogue Multimeter and Digital meter. What are we adjusting, the Rich/Lean screw in the Filter housing? or the EHA screw.
With the air flow meter test, are we adjusting EHA screw or the Rich/lean screw.

Please advise
Brian

PS: I'm at a point now where I would like to fix this thing or go to alternatives like this one.....
This note from the Mercedes Workshop Manual that discusses "Vibrates at idle", in effect says that you can glean another 50 rpm out the CIS by splitting a wire that runs from the Starterlockout switch to the CIS, and connect the CIS end to ground
It seems to me that Mercedes recongised some time ago that idle adjustment is a complex problem and even if all the parts are working you may still have a problem with idling per specs. Sooooo, they came up with a couple of mods? This one and the resistor in the CIS temp sendor circuit.