Re: Questions on Misfire on '07 Navigator w/5.4
Others may disagree, but I'm a little bit old school, I'd pull all the plugs and do some comparisons. If they all look beat, replace them all, if just number 7 looks hammered, you may have another issue going on. Newer plugs run a lot longer than the old, the ones I just put in my truck are suposed to be good for 100K and it has a '92 engine in it.
Chewing on asphalt and drinking dinosaur wine