Oldsmobile/Buick Repair: 96 Lesabre cuts off, port fuel injection, oil pressure switch

Question
I have a 1996 Buick Lesabre Limited edition 144K ran great until 2 months ago. It began to jerk violently when in idle and cut off intermittently, and restart on the 1st try. I took it to a shop and they replaced the EGR valve and gave it a tune up. Two weeks later the car started cutting off again as many as 3-4 times in 10 minutes. I took it back, and they ran a diagnostic with no luck, and drove for 30 min and problem did not duplicate. 1 week later the check engine light came on and began to idle violently, took it back and they replaced the MAP sensor. My problem is that the car keeps cutting off, a/c on or off, stopped at light, accellerating from light, mostly low speeds, also dies on start up occasionaly. it  is very distressing. While driving/start RPMs surge irregularly. When it cuts off the RPMs go up a little and it dies, it is smooth, no noises, smoke, or roughness. I am in need of your assistance please advise.

thank you
cherie

Answer
Hello Cherie,
I would get a fuel pressure tester, and connect it so I could watch the gauge while driving.
The pressure needs to stay up within specs. I believe you probably have Multi Port Fuel injection,(MPFI), so the pressure should stay between 28 and 32 PSI while running.
If the car dies, ideally the pressure should drop AFTER the engine dies.
If the pressure surges or drops while the engine is running, even running bad, then the fuel system is where I would concentrate, because there is an oil pressure switch that keeps the pump running as long as there is at least 4PSI of oil pressure.
If the pressure stays within the running specs, then the pump and pressure regulator are not the problem.
If you have a different system than MPFI, the pressure could be different, but that is what I believe that car has.

If the EGR replacement fixed the problem before, it is possible that there is some carbon breaking loose, and causing it to not seal. It shouldn't need replaced, since it is an item that can, and should be removed and cleaned.

Those are where I would start.

Good luck,
Van