My 5.4L runs great 0-60MPH under normal driving conditions and acceleration. But if I punch it from a dead stop, or try to accelerate hard to change lanes on the highway the engine hesitates, knocks, and does not take off. I would have thought that putting the pedal to the floor would slam my head against the headrest. After these events, the engine light blinks for about 30 seconds, then turns off. I took it to the Ford Dealer and they said the engine code said the #3 plug or coil was bad. I didn't change it immediately. Would a cylinder not firing correctly cause this hesitation and lack of power issue? When I decided to do it I took it back the code was not there anymore and they advised that it was not worth it. With Ford's brilliant design of plugs/coils/heads it would cost $350-$400 to replace all 8. The truck has 91K miles. Should I just suck it up and replace all 8 now and see if that remedies my issues? Please be nice, I am new subscriber and not a master mechanic.

 

If you have 91k and have never changed the spark plugs, it's time! Make sure whoever does it is aware of the TSB and issues. It may need one or more coils too.

 

Bad plug or coil pack would certainly make it act in such a way. If their the Stock OEM plugs, i'd suggest getting them replaced ASAP.

 

I was haveing the same problem. if u let it go on too long it'll ruin ur C.Coverters. trust me Im paying out the butt on it right now. take it and have the plugs changed ASAP!.