Gentlemen,
I believe I got the solution to the problem on my benz, it may or may not be pertaining to your benz's. The problem I had was just as described, you start the car, it idles perferct for a few minutes, then the temp rises and and the miss/rough idle begins. Sometimes when driving and you initially step on the accelerator pedal, you feel a tad bit of hesitation for a few secs,when you are stationary (at a light or something) the car will also tend to shake due to the miss. After changing the plugs about 11.000 ago (platinum 4's). the Cap, Rotor, Ignition Wires (Quite Recent). I last week pulled out the plugs and each and every one of them was black ( I mean black). I wondered whether this was because they were Platinum 4s and they are not really recommended on the older benz's as I recently found out , or whether it was another issue. I changed the plugs to the regular Bosch Super's and didn't notice any difference. Today I pulled out the Idle control Valve and replaced it with a used one from a parts car, I drove the car round the block and sure enough, it was humming. It was music to my ears. I actually just got into the house from a drive, I just sat in the car listening to it hum. This may be one of the problems one of you guys is going through. But make sure you know it is the Idle Control Valve before you spend the $295.00 for the little sucker!! Yup that little sucker is expensive. if you know of any parts cars anywhere you might want to check them out prior. I figure the other parts that I changed needed to be changed anyway, except for the wires which I think were fine!!
I have an 83 380sel (Euro).