Originally Posted by Jeffreysan
So I've got a 1997 F150 XLT, 4.6l V8 w/140,000 miles. I've drive it 70+ miles a day, and I've had a recurring missfire problem. The spark plug boots pop off regulary. No matter how hard I push them down on the plug, they still work themselves back off. It used to be random, that is, any one of the boots would jump off, but now it seems to just be cylinder 3. I changed the coil pack some time ago, and just did the plugs and wires last weekend thinking it was just a bad set of wires. NOPE- on my way to work this morning the number 3 started missfiring; I pulled it over and sure as you-know-what the plug boot was not secure. HELP! This is driving me friggen nuts! I'm a decent mechanic, so I'm not totally lame when it comes to maintaining this truck, but this one has me stumped.
I had the same problem with plug boot popping off.
Ford has a problem with the spark plugs stripping out. They blame it on over torquing but it happens on vehicles that have factory installed plugs. Worst case scenario they eject and have caused hood fires.
My guess is that the plugs have backed out and/or the threads are stripped allowing blow-by which builds up pressure and pops the boots off. It can also split the boot causing spark arc.
If you change your plugs and find some have seized, back them out just a little, spray in anti seize, leave overnight. Also back them out and in a little, then out more and so on to help clear the threads as you remove them....I have considered applying Loctite to the plug threads to seal them off.
I'd like to know the rocket scientist that designed that motor. They place it so far back in the engine space its impossible to work on the two back plugs. Just 3" ahead is all it needs.
Mine has 190K and what I saved in maintenance I have spent on fuel.
BTW I am chasing a miss fire as well...It's so much fun changing the wires which are buried...Not!