Pontiac Repair: 2000 Grand Prix GT 3.8 litre, grand prix gt, highway speeds

Question
At Highway speeds only, when i accelerate a little hard the RPM'S go high and low rapidly, and the car jerks a lot hard, if i keep on it engine light will flash, lower speeds it runs perfect...What could this be? Thank you

Answer
Hi
It is a misfire. Since the light is flashing you need to have it adressed NOW. Flashing light means it is in a catalyst damaging range.
I would suspect if you preformed a good major tune up (Plugs, wires, fuel filter, air filter) and check the coil towers, and repalce any that are rusted or corroded, you'll PROBABALLY fix your problem.
As I must say though, this is JUST advice. If you took it to a paRTS STORE (AUTOZONE, NAPA, Advance) and have the code checked or a repair shop, just to make sure.
Thats my advice.
I hope it helps
Good Luck
God Bless
Pawl