Ok, I checked the fault codes and the figures to gave me show that all is ok with the switches (10%, 20% and 70%).

Run the engine till hot then shut it down. Press the air flow plate down and smell inside. If there is a strong smell of fuel then the seal at the bottom of the fuel distributor may be leaking fuel into the manifold (explaining the excessively rich mixture at idle)

Otherwise I'd just try leaning out the mixture a quarter turn at a time (remember how many turns you do) until you get it back between 30-50% at hot idle and 50% at 2500rpm.

Was this problem sudden or has it slowly been getting worse?

__________________
Alex.

MB Tech
Sydney, Australia
Volvo 122S
W201 190D 2.5 manual
W202 C240
W203 C32