Hello. I'm trying to fix my mother in laws 2001 Lesabre. It will start and run for a couple seconds then die like I turned it off. It died while she was driving it. Had it towed wouldn't start. I went out to work on it but it started up and ran. She drove it a a couple times then it died again while driving it. Now it is stalling again after starting.

I tried unplugging the maf. No change.
Since it does fire and run for a couple seconds I don't suspect the crank sensor, I did try unplugging it to see what would happen and as I expected it will crank and not fire.

I read some where that if the oil pressure switch is failing it can shut the car down after starting for a couple seconds.

The car does have oil. I tested fuel pressure and it was good. I tried swapping out fuel pump relay-no change.

No codes. No security light. Does not have a ignition key with a chip in it.

Any ideas?