Hey, I have a 2006 Pontiac Grand Prix GT. Supercharged 3.8 L engine.
So far I've changed the fuel injectors, spark plugs, wires, coil packs, supercharger bypass sensor, evap solenoid, ignition module, all fluids, downstream 02 sensor. No change in the acceleration. Still a strange jerky acceleration. Goes to about 60mph and the check engine light blinks. There's also a small thud while idling. The diagnostic read a cylinder 3 misfire but still can't find out why? It's all brand new. Any help would be appreciated. Thank you.
It’s definitely a misfire by the sounds of your problem. Next step would be a cylinder leakage test or compression test on that bank to see if #3 reads differently than the others. Aside from that the parts may be new but the electrical to them is not so I would still verify spark and use a noid light if available to verify spark and injector pulse is actually present
Why keep throwing parts at the problem? Start with the basics; MAF, air cleaner, MAP, TPS, fuel pressure, electronic throttle control motors, etc.
