vibration
 

I was just listening to my daughter back out on to the driveway and in her 87 300e and it seemed to run a little rougher than my wifes 85 500sel. Is this just the way it is? I think both idle just at the correct rpm, but the six just seems to have a bit of vibration at low speed in gear.

Rough idle can be caused by many tings such as slightly clogged injectors, motor mounts, to real engine problems.

I wold start by using some good fuel injector cleaner (Chevron Techron) and double dose it.