We ran an OBD 2 code reader on our 97 GP and found that it had multi-cylinders misfiring. A mechanic suggested this was a simple tuneup. After changing plugs and wires we've attempted to start it and appears to want to start but the motor simply wont start. We manually turned the crank with a socket on the harmonic balance wheel to see if the motor was seized and it turned fine. We also did this after pulling a plug and putting a screwdriver in the plug hole and the piston pushed it back out so again we believe its not seized. We pulled the starter off the car, took it to the automotive store to have it bench tested and they say the starter is fine. The battery also is fine. Help... Does anyone have any ideas??

Verify that you have the wires in the correct firing order: 1997 Pontiac Grand Prix 3.8 liter V-6 VIN "K"

If they're correct, check for spark on several plug wires. If no spark then you have either a bad ignition module or crank sensor.