I have a 2004 ford f150 5.4L super cab xlt 4x4 and I have been running into a problem when accelerating and reaching high speed. The problem is when I floor the accelerator the truck would pick up speed but it will feel a bit sluggish and when it reaches 70 mph it will flash the check engine light. Also if you try to accelerate while its flashing it will shake hard. When you accelerate normally the truck can go passed 70 mph. When I check the code it has pending p0305. I have changed all spark plugs and ignition coils. Also every now and then it has a hard slip and kick feeling when going from 2nd to 3rd gear. Please I would appreciate any help.

 

Retorque your plugs to start - pretty common for them to come loose. Also may have a bad plug - I've seen anywhere from 1-3 bad plugs out of the box on one change before. Double check that all coils are seated properly as well.

 

i agree. you are misfiring bad. could be a coil wire has a nick in it also. this happened to me. check your wires on the rear passenger side next to the firewall. this wire rubs up against the a/c high pressure side and melts the wire lining away leaving it exposed to short against the a/c line. when you are WOT the engine leans back and causes contact. This will also cause your truck to feel like your transmission is slipping. When it shorts out causing the misfire it also screws with your PCM because that particular wire is also tied in with your A/C compressor and other things.

 

Misfire on 5 it's either the coil or plug. Try swapping coil to another cylinder, clear code an see if it repeats on same cylinder. If yes it's plug if no then it's wherever you moved coil to.

 

This. Also verify the coil is sitting on the plug properly.

 

have you looked at your FPDM (fuel pump driver module)? You could be losing fuel pressure and this cause the misfire. The ECM figures its a misfire cause the crank speed is slower than it figures

 

another thing to look at ...did you us Dielectric grease as required.. I would also check the condition of your FPDM...very common problem.

 

I'm going to check the fuel pressure and try flipping the coils and changing the plug in cylinder 5. They also told me it could be caused by clogged cats but the truck runs perfect the whole time. It only has that slip from 2nd to 3rd once in awhile and when I floor the accelerator it blinks the engine light at 70 mph. Ill get back to everyone if I have any change or not THANKS for the replies!!!

 

I'm gonna check all the wiring on the passenger side any suggestions on the what to look for exactly like a little more specific thanks.