Have a engine light on for misfiring

Scan for the trouble codes to find out why the light is on. An auto part store can do this for free, post the codes back here. Misfire codes will be P0301 through P0306. The last number of the code corresponds to the cylinder. 1 through 6. So P0304 is cylinder #4. If you swapped the plugs and still have a code, I would suspect the COP or Coil on plug is the issue. Try replacing the coil on the cylinders that are showing the code.

I had issues with my grand prix not picking up speed, after changing plugs, wires, sensor, plus. Finally a friend checked the catalist converter, it was dirty, bad. Got it cleaned out, welded back on, things have been good since.