I recently purchased a 2006 F150 with a 5.4. It's got 200k kms on it. Transmission was just rebuilt. I've just changed the spark plugs and one coil to fix a minor mmisfire.theres is no CEL. But every now and then while driving, I'll feel a slight vibration. Not sure if it's a misfire or if something is out of balance. The truck idles smooth and accelerates smooth but sometimes just cruising down the road I'll feel it. Maybe 30% if the time. It comes and goes. With no CEL I'm not sure where to begin looking. I've not had it very long. Only put about a half tank of fuel thru it so far. I plan to do an oil change this weekend.

 

What brand plugs did you install ? you may need new boots and springs for the coils.

 

You need to do a mode six check . It will tell you your misfires by each cly building raw computer counts toward setting a code. Zero counts is what you want and is achievable. Ford set the code threshold quite high to prevent nuisance codes . This way you can go to the cly that is in trouble .