Hi,
Car is w124 220E '93 with 2.2 litre 16 valve type M111 engine with automatic transmission. This engine has motronic HFM fuel injenction system. Problem is here:
Sometimes engine is running poor when pressing accelerator pedal about
10% -> rpm's go from 500 to 1500 very regular unless you left engine to idle speed witch it runs fine. If you press pedal so much that engine reach 3000rpm there is never no problem, it's running fine on those rpm's . When this fault is "on" its impossible to accelerate smoothly because if you press acelerator pedal little bit nothing happens. When pressing accelerator more then car suddenly starts accelerating, this is very unconfortable on the road.. :(Sometimes when running steady 55mph engine stalls like turning ingition off but if you press gas pedal immediatedly its accelerating fine unless you try to go steady speed it stalls again...
Car always starts very good when engine is cool or hot.
I take off idle speed control unit and put contact cleaner to the conponents, this helps a while (about 1000km), then problem comes up again. Below are links to pictures I take from idle speed unit. I think problem could be contact failure on that white round component because when putting a lot contact cleaner to the root of the axle car is running good a while. This looks you can do nothing to fix it because accelerator lever mechanism is welded on both sides.. Any ideas? New idle speed control unit costs about 600 euros (over 600USD) and it would be waste of money if only one component is broken but if you can't fix it you must pay..
Pictures of the unit: