why does car stall? on 1991 Buick Riviera

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
car has about 110,000 miles has only stall 4 times in 2 months
(2) Answers
There are 2-3 things on theses cars that fail a lot and cause intermittent stalling.
1 the crank sensor 2 the ignition module and last the power train computer (ECM). I would have a good pro shop check these out in this order. It is pretty simple.
There a quite a few things that can cause your engine to stall intermittently. One question to as is - Does the engine stall when you let your foot off the gas or coming to a stop? If this is the case then the cause could be a dirty throttle body or sticking idle air control valve. If the engine stalls on acceleration then some possibilities are are a faulty crank shaft position sensor or mass air flow sensor. If the engine will not restart right away that might indicate a faulty ignition module. The powertrain control module is also a possibility in any of the above cases. There can be a lot of trial and error in trying to isolate the cause of an intermittent stalling condition. Any stored fault codes in the powertrain control module may help.