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:
http://img6.imgspot.com/u/04/234/12/idleproblem.jpg
http://img6.imgspot.com/u/04/234/12/idleproblem3.jpg