I just bought a 2006 F150 Harley Davidson edition with the 5.4 engine. It has 92k miles. It idles fine, accelerates at half throttle no problem but has a miss/hesitation if you let off the gas then accelerate again. Also will not accelerate at WOT. It will bog down, hesitate and backfire. If I feather the throttle it will clear up and accelerate. Bought it from the original owner who changed the plugs at 80k. There are no codes and no check engine light.

I pulled a couple plugs and they look newer. On one plug only the nut came out leaving the plug in the head. See pic. I take it I will need a lisle tool to get out? Looks like it is in one piece except the nut. I'm assuming the plug is no longer good. I screwed the nut back on and it runs great except the WOT bogging and miss.

 

Yup, and sounds like you may need to do a throttle recalibration and possible a throttle body cleaning.

 

I did clean the throttle body and do the recalibration. Going to change the plugs today. Hopefully that solves the WOT problem.

 

Looks like you'll also probably have to break off the top of that plug to get the lisle tool in there.

 

plugs should come right out if they only had 12K miles on them...wonder if they are SP515's ??

 

2 of them did but one only the nut with threads came out leaving the whole plug behind. They are 515's. Maybe this one was never changed.

 

maybe ?? when you get it out let us know what it was.

 

I will. I need to get the Lisle tool. Will probably tackle this next weekend. I'm hoping this plug is what's causing the WOT problem.

 

Ok....while driving to the airport last week I got a code (finally). P0420. So now I may have a plugged passenger side cat. Got home last night and today I changed all the ignition coils and all spark plugs except #5 (1st plug on drivers side). That is the plug where only the nut came out. I took it for a drive and what a difference. No more hesitation at all or bogging on full throttle. When I get the tool I will replace the other plug but for now it is running great! Still need to check the cats though just in case it got damaged from the misfired.

 

I'd think if the cat was plugged, you'd still be chugging, but you're saying there's no hesitation or bogging. None at all? Then aside from the code, why do you think it's plugged? I say clear that code and see if it comes back now.