i was drving my car the rpm was at 2X1000 and then i was going 65 the rpm went from 1-4 back and fourth and the car wouldnt move it died. we replace the throttel posttion sensor and it still didnt help the car will still go from rpm to rpm and it wont do anything and it wont turn on but then a few min's later it will turn on i ahve no clue wahts is wrong and i need help.

 

Have it scanned at a reliable shop or GM dealer. It could be the VSS - vehicle speed sensor. It could be other stuff too.