My 1991 420SEL (78,000 miles) has a sudden pulsation in the idle at stops. Has been reciently tuned/maintained but didn't stop the idle pulsation. The range of pulsation is only a few hundred RPM. Also seem to have rough start problem when outside temp is hot and car has sat for over an hour (also bad exhaust smell outside after hard start). Any suggestions on where to look?
Thank for your help!