300E rough Idle
 

My 1989 300E will idle rough when I stop for a light and resume, as if it was running on 4 cylinders. I will floor the Accelerator and it will run fine until idle again. I let it idle with A/C on for about 5 minutes and when I pulled off it began to smoke(couldn`t tell if blue or white). After smoke cleared it ran fine. Please help!

Could be anything from ignition to fuel problem. Best bet is to have the engine scoped and narrow down what cylinder it is.

Idle problem
 

I agree with euro 287;) get the scope done or at least a wet/dry compression test and give us the results. If the test comes up with one or more cylinders very low on the dry test then the wet test they look much better you have bad piston rings. If they are good through out we will start looking at fuel and ignition problems. How many miles are on the car ? What is some of the past work you have had done ? Any engine work ?