my 2004 f150 is running rough and its not the sparkplugs and it turns off and backfires
Problems could be many and varied. A backfire occurs either in the exhaust system or the intake system. But it occurs outside the combustion chamber/cylinders. Unburned gasoline exiting the chamber may ignite once it hits the hot catalytic converter. If a valve does not completely close prior to detonation it could also fire backward through the carburetor or intake manifold. Have the vehicle towed to a qualified repair shop for diagnosis. You can damage your vehicle with such a condition. It is possible the catalytic converter is already shot. No big problem unless your state test exhaust gases for annual inspection. In that event you will most likely fail.
Search Ford F-150 Questions
Ford F-150 Experts