The car is a 1993 850 GLT, manual, with 111k. Bought the car at 98k. Stalls and almost immediately will restart with key, but apparently not by popping clutch.

The first time it quit the day after I bought it. The next time was months later; quit 6 or 7 times in a 100 mile, two hour period. One of the stalls was accompanied by the 'recirc' and 'ac off' lights flashing for a minute, and the 'check engine' light coming on and staying on. The smooth transition between 'accelerate' and 'decelerate' is no longer smooth. A local dealership wanted to sell me an air mass sensor, since the code said there was a problem there. I resisted since I hate to throw $300 to finance their shopping around in my engine compartment. The car ran fine for two more months. Started again on 9/11, once a week or so. Now seems to be having the problem more even more often (5 times this past weekend, this morning). No idiot lights light, no warning, always restarts (so far), just like somebody flips a switch. Doesn't stay dead long enough to try diagnostics like looking for spark or no fuel.

Ideas?