Proud owner of a 92 400E with 180,000 miles.
About 1 month ago my cruise control stopped working, about a week later a rough idle at cold start began. The rough idle has become progresivly worse over the last few weeks to the point where the car will start and instantly die.
Here is what I have done so far:

In the mornings (cold start) I have to keep the rpm's up for a few mins until warm then the idle drops down below 500 and almost dies. I am noticing vibration coming from drivers side of engine compartment until engine is fully warmed up. I also see a distinct loss of power during the cold start, dim lights, slow to pick up speed and almost stalls. After car is warm it starts and drives like normal apart from a slightly rough idle.

Replaced plugs, distibutor caps & rotors. After I did the caps and rotors she started up normally but then the following day was back to the bad symptoms.

I looked around the forums but could not seem to pinpoint a thread to help rectify this problem so any help would be greatly appreciated. Also I am by no means an experienced mechanic, but can handle the basics and willing to learn new things.

All the best,
Luke H