my bro has a 1990 cavalier, it quit on him at 65 mph still has spark and fuel and it will start for a few seconds but then dies. he let it sit for three hours and it ran fine all day but then did the same thing the next day. What could it be? IT is a 2.2 fi. auto just tuned up and fuel filter was changed a month ago.

Does it have fuel pressure past the three seconds that the pump is on when you first turn the key on?

I believe the computer controls the fuel pump after startup on that car, so it might be best to pull codes and see if it's shutting off the fuel itself or if there is a loose wire.

i was also voting for fuel shutoff.there is probably a button, valve or whatever somewhere that has been tripped.