1987 420SEL idling problem
 

A friend of mine has a 1987 420 that has a real aversion to idling. Actually it only starts if you have the air cleaner off and you apply a small amount of pressure to the door on the fuel distributor. It seems as though without a finger pressing the door down, the car will just turn over but never start. Once it is running you can keep it running by stepping on the gas or by keeping a finger on the door. It cuts off as soon as you remove the finger or take your foot off of the gas.
Does this sound familiar to anyone?

The fuel mixture is out of adjustment or you have a bad vacuum leak.