I am new here, I have a 02 f150, 4.6 l, and I have a spark plug in the #4 cylinder, that I can’t break loose, it’s coding out to a misfire in the #4 cylinder, any thing will help!!!!

 

Because of Ford's fix to a design issue with plugs, the threaded area has been made longer than needed and a small portion extends into the combustion chamber where carbon collects on those threads, making it hard to back off the plug. If you can loosen even slightly, spraying some solvent into the plug hole might soften up the carbon. I often use PB Blaster which works well. If you can break it loose, you might want to work the plug back and forth as you loosen like you were working a tap.