I have a real mind blower. My friend has a 2003 Buick LeSabre 3800 with approximately 80000 miles. He complains that the car will die while he is driving. I work at a local parts store and have access to code reading scanner. We’ve checked the fuel pressure at fuel rail several times and is okay. The only thing that seems odd to me is that he says the tach will quit working. It dies like the switch has been cut off. He can wait, sometimes 10 to 30 minutes, and the car will restart. I had him to come by work when the car acted up so I could scan it. It gave crank sensor out of range, and indeed the tach was not working. I turned the car off to scan, and restarted. The tach was working.
Mr. Obvious, Here. Have You Considered A Possibly Intermittent Failing Crank Sensor / Sensor Circuit ?
Crank sensor, crank sensor circuit, or ignition module/circuit are where you will find the problem. Hopefully it can remain in failure mode long enough some time soon to figure it out. The tach not working when this issue arises narrows it down a lot.