1991 Buick Lesabre Car will shut down while driving

Engine Mechanical problem
1991 Buick Lesabre 6 cyl Front Wheel Drive Automatic

The car would shut down and then would not start.
Sometimes you could let it sit for a while and then it would start. When the check engine light came on the diasnotic check said the Cam Shaft sensor was bad. This was replaced and didn't help. Replaced the Crank Shaft sensor, ran for a month or two and began to do the same thing again. Replaced the Crank Shaft sensor again. Car ran for about two weeks and began shutting down and not cranking. Replaced the Computer, ran perfectly for a week and then while driving it shut down. I tried starting it about 7 times. When you stoppped trying to start it it would back fire. It finally started, I drove it home, about 3 miles. The next day it would turn over but would not start. The next day it started and I drove it for about 30 minutes, and while riding along it shut down as if it lost all fire. I sat or about 10 minutes and it finally started and I drove it home about 400 yards. It has been sitting since then. About 9 month ago it would not start and I replaced the coil pack and it ran good up until it started acting up again.