Car stalls periodically

My wife has a 1989 Cutlass Ciera w/6cyl. It runs very well most of the time. But periodically, it will act like it stutters then stalls out completely when coming to a full stop. It will crank up immediately in neutral but stalls again when put into drive (it will shift into reverse :banghead: without stalling). The problem seems to go away after the engine cools somewhat. It has a new fuel pump, fuel filter, plugs, etc. The auto repair shop has not been able to duplicate the problem when checking out the car (it simply won't cooperate when being looked at by a mechanic). I would appreciate any helpful advice anyone could give me to either fix the problem or clue the mechanic as to what to look for. Thanks. :banghead:

I had an occassional problem with my four cylinder cierra; it would stall and not restart for several minutes. It turned out the crankshaft position sensor was cracked.