I replaced the cop for a 3rd cyl. Mis fire and the truck barely runsin idle will still fly down the highway but have to bulldog it to keep it running at a stop its a 4.6 ... Any ideas

 

The COP is not the only thing to cause a misfire, did you at least pull the plug and check it out when you replaced the COP? Also inspect the boot for cracks. Make sure that the connector to the harness for the COP is seated in good and snapped into place.

Good luck.

 

Thanks anyway