My 87 190E 2.3-16V has been in the shop repeatedly for start and idle problems. My mechanic doesn't seem to know how to correct the situation. Please help.

Cold start: car starts up and dies immediately, as if out of fuel. This continues until I give some pressure to the throttle, but the engine will not idle without continuous pressure on the throttle.

Hot start: after car is hot and engine is turned off, same starting problem resumes.

First drive: when the car is first driven, for about a quarter mile it coughs and chokes as if there is vacuum loss. (I am not mechanically inclined so "vacuum loss" may be incorrect description and may be misleading. Apologies, if this is the case.)

Once the car has been driven for several minutes the idle settles down at 1300 RPM (not at the 900 +/- 50 specified by the factory).

Above problems occur regardless of a/c being on or off.

My mechanic has already replaced 1) throttle valve; 2) air flow position sensor; 3) potentiometer and then my a/c compressor had to be replaced (????) when the a/c stopped working during one of the repair trips.

It is most frustrating. Thanks in advance for your comments and help.