2001 Buick Regal cuts off while driving at times also won't start

Is it possible you might have installed the thermostat upside down? How long was it hot? You might have burned your engine up. Check compression, each cylinder should be over 100 at least, and around 130 at best.

try replacing your ignition module the grease that keeps it from overheating has probably dried out

Could be a dirty throttle body or a faulty idle air control valve.
The computer controls idle speed by regulating the amount of air entering the intake thru the throttle body.

I would replace the crankshaft ignition pickup (Crank position sensor)

I WAS TOLD THAT SOMETIMES 3.8L IF IT HAS ABOUT 150K MILES THE TIMING CHAIN GET SLOPPY AND CAUSE;S THE ENGINE TO DIE !!! THEN START WHEN IT COOLS OFF ???

the batt is suspect...take it to autozone, or other place, they'll check it out free......the shifting out of park is a seperate issue, the pawl for the steering/shifter is not working properly....did you notice if the steering wheel would turn when the shifter is stuck?....probably not....when this happens try to turn the wheel back and forth-not hard but not gently- a little graphite dust sprayed in there would help.......hope this helps you out

egr valve is not opening up when the engine reaches it normal operating temperture

test the EGR valve.

hi is it automatic and won,t start that mean won,t turn over or turns over but won,t start ? how occasional yates210456