Originally Posted by
zip439
Exhaust Gas Recirculation valve (EGR) will cause rough idle when it is stuck open. For the first three minutes of operation the auxiliary pump is probably running and the car is in closed loop; after three minutes it goes to open loop and the stuck open EGR valve may be your problem.
Thank you zip439. Since I'm not getting any fault codes is there a way to check the EGR valve for sticking open? FCP Euro has the genuine Mercedes for $188.99. I don't want to start throwing parts hoping that is the problem.