I am at my wit's end with this problem. I have a 1992 400SE with almost 89,000 miles.
It cranks fine. When I come to a stop that last more than about 30 seconds, the car begins to idle so roughly that the car is shaking. If I try to accelerate, the engine continues to run roughly and the shaking continues. There is a definite loss of power and the car is struggling to run. The only way I can correct the problem is to turn the engine off, immediately restart and it runs fine. The problem might begin again with my next stop, or may not.
What is frustrating is that this problems is intermittent, but is getting worse. My shop has observed the problem.
The first thing done to try to correct the problem was the additon of a fuel cleaner to the gas tank. Did not work.
I just got the car back from the shop 2 days ago, after a one week stay 60 miles from home. The Wiring Harness was replaced under warranty by MB, thank goodness. Also, a new Crank Sensor was installed and positioned. My bill notes "Run DTC found code for crank sensor, replace sensor". The senor was $171.32 and "positioning" cost was $163.80
The car ran fine for 2 days and today the problem returned.
The idle problem is not related to how long the car has been running. The problem might occur 5 minutes after the car has been running, or one hour. Wet or dry, hot or cold conditions do not seem to matter.
Please help! This is driving me crazy.
p.s. I am female, so please reply in "non-tech" language.