I have a 2006 F150, 5.4l, FX4 SuperCrew that has developed some misfires issues. I have been able to pinpoint when it does it. WOT on a cold engine, one the engine heats up it drives fine. Doesn't do it on light load on a cold engine, only on WOT which I don't do too often because I like to try and conserve gas. No check engine lights, was thinking about unhooking the battery to see if that would do anygood, not sure it would. Just had some wiring repaired, wires going to cam sensor were cut when my serp. belt got eaten. Not sure that has anything to do with it either.

Anybody know what the cause might be? Thanks in advance!

 

how many miles on the plugs? I had an autolite HT1 cause a misfire after 13,000 miles. Switched them all out for Motorcraft and all is fine. Took a while for it to throw a code.

 

Original plugs with 40,000 miles on them. I was thinking that might be a possible cause but never had a problem with plugs on other vehicles I've owned. I'm a little leary of taking them off myself because of all the problems I've read about people breaking them. Just thought it was odd that it only did it when the engine was cold.