About a month ago I replaced my MAS in my 2000 C230k. I got the CE light warning; confirmed the error code and replaced it. Being that it was the original (replaced it at 97000 mi), I did not think much of it's (the original's) condition.

Well a month later, I have other performance issues: Often my supercharger just turns off. The car has experienced worsening hesitation. I've done hours of forum research and repalced, plugs, fuel filter, fuel pressure reg., air filter...

After changing out the fuel pressure reg (today), I got no better results. BUT I noticed something that caught my eye; my month old (new Bosch) MAS had oil around the out side of the base. So I take it off and WOW it is all oily on the inside. The screen, sensor the walls... even the air tubes are oily. So I take a rag, wipe out the air ducts, then (gently) wipe off the MAS and then take some compressed air (45 psi) and blow off the sensor etc.

I hook it back up, drive it around after 10 minutes the hesitation starts to go away. The supercharger kicks off a few times but I have a cure (I have to stop, put the car in neutral, turn it off then back on again to reactivate the supercharger - this is VERY frustrating).

So my questions are:
1) where is the oil coming from? Could it be from the supercharger? Or blow-by oil from the one of the recovery tubes (head, dip stick etc.)?
2) Isn't the MAS suposed to be "dry"?
3) Could oil on the MAS affect the performance, thus telling the system to zag when it should zig all because of the oil?
5) could the supercharger be leaking its oil (thus going bad and needing replacement)?
6) What do I do next?

Shawn