My 2004 Pontiac Grand Prix with 58,000 miles on it. I have trouble startimg it, when I turn the key in the ignition the engine will turn over then die or not turn over at all. I can force a start by gently pumping the gas while turning the key. Also, while driving at highway speeds; the RPM fluctuates causing me, the driver, to feel a noticeable change in momentum. I have changed the fuel filter, but no improvements were observed ? any ideas on how to deal with these concerns?
Probably a little late, but clean your throttle body, and maf sensor. mine did the same thing for a short period, would run fine once it was started and going.
MAF sensor or weak fuel pressure (failing fuel pump or restricted fuel lines).