For starts Hi, Im new to this forum and solely because I just bought a pristene 2006 F150 Supercrew 4x4 XLt. This is the first Ford I have ever bought. I noticed the other day when I was driving there was what almost felt like a clunk, if I had to describe it I would say it felt like the truck was bumped while driving. It only happened once then then next day it happened a couple of times within a 15sec time frame. I have narrowed it down to crusing at 45 or 80. I have also noticed when under hard acceleration is has a slight roughness. Im assuming this is a misfire maybe but there is no check engine light comming on at any time, and yes the check engine light does light up on initial startup for system check. Im worried that this could be something with my overdrive. Any suggestions or help would be greatly appreciated.
Oh and by the way the truck has 81k miles, unknown if the plugs have been changed and im dreading that as to what I hear about the two part plugs comming apart. I do my own maintance..

 

i had the same problem with my 06 screw lariat 4x4 5.4. i thought my trans was going but eventually check engine light came on and it was coded as mis fire cyl 2, reolaced coil and truck ran great.. lucky that was an easy one to get at.. well 6 months later (now) truck is doing it again.. no light or code yet.

 

Before you do anything buy a good code reader, check your codes, record your freeze frame data, save it and also your I/M sensor tests. Keep these for future needs. After documenting your data erase your codes reset your your puter by disconnecting the battery cables. After driving and letting the puter re learn, then check for codes again and make your maintenance. You will always have the data to re check if you have furthur problems with the truck. Reason to buy the quality reader is for your information and to save you a lot of migrane Threshold level adjustments later. Also rent the lisle tool for the tune up phase of the project.

 

Thanks guys for.the info. My only question is it happens everytime i drive it but only at 45 and 80 with accelerator pressed only enough to maintain speed. Oh and under hard acceleration yet it has not triggered the engine light or stored any codes. My only gurss is wait until that happens because it would be alot of work to buy one coil and swap it around until i get it right. Agree or any better suggestions.

 

My 05 was doing the same thing. I also dreaded the plug change, but I did it and it runs better than new. my idle was rough and I didnt know until after the plug change.

 

Drop your spare tire and see if you have a corroded fuel driver module. These get bad and let moisture into the internal electronics starving the engine of fuel.