Car problems.1992 Buick LeSabre 3800 V6.The car is shutting off and and

[Deon]

turns back on immd. Nocheckengi lighto? My car will crank when it wants to and shut down when it feels like it.. More so after it has warmed up for a few minutes. The check engine light doesnt come on often but occasionally not enough to get a diagnostic done. The milage is 122000 and I had a mech check the veh and he couldnt diagnose the problem ( leaning crank shift ). I have other leaning Mass Air Flow Sensors and Fuel Pump. I dont want to buy all 3 parts to try I looking for more insight on the problem. I did have a problem with starting but i think i was because of a loose starter solenoid i replaced personally. I also had the batt, alt, and ign coils checked and all are good status... Please insight me