OK, working on my brothers expedition today with my dad, as the expy recently blew a plug. He had gotten that one fixed, but we were looking to change the other plugs since they had 140,000 miles. Came across the plug on the passenger side, 3rd one back. This may be the one that blew out about a year ago and was fixed by Ford, but we aren't sure. We got the coil out ok but couldn't get the spark plug out, because we couldn't get the socket on it! After about an hour of being frustrated whipped out the flashlight and the mirror and looked down in the hole and there was an obstruction... we could clearly see the plug and about half of the flanges for the spark plug, the other part had something covering it. As we look further, it looks like a piece of metal that is the perfect size that it fits in the hole over half the spark plug, looks like its cut to fit even because it matches up on the spark plug side just right and on the hole for the spark plug hole. We can't get it out (have been working about 3 hours now) and because its in place, we can't get the spark plug out. ABout to light the thing on fire and roll it down a hill.
Does that sound liek a fix that a mechanic or dealership might have put in place to keep the spark plug from blowing again?

 

With a few tries & a decent camera, you can get down in there - I did:

 

yeah unfortunately my camera was away, but it wouldn't have done much good since it was actually under the firewall, the only way we could see it was with a mirror and even then it was hit or miss.
Long story short, it wasnt anything Ford installed, it wasnt anything metallic. It was rubber, and had apparently been there since Ford did their change but we have no idea what it is, it almost appeared to be part of a boot, but the boot we took out was perfectly intact. We spent about 6 hours on it yesterday and managed to get about half of it, we are going to continue working today. The problem is, we can't really see if and when we are poking around for it, ,cant even really feel it, though we know it is there..

 

I'll take a wild guess - it could be the interior rubber portion of a spark plug socket. Must have broken off when they were putting in the replacement plug. Now it has baked in there.

 

I've had to deal with that once on a Quad 4 about 13 years ago.

I took a 5/8" SP socket and removed the rubber insert, heated the socket with a butane torch until it was smokin hot, inserted it onto the plug and seated it all the way down on the plug (melting the rubber as it went), then let it cool.

Took the plug right out along with all the rubber about 2 hours later.

I thought about trying to chip the rubber out of it to salvage the socket, but the heat ruins the temper, so I just tossed the socket in the trash with the plug still in it.

You don't want the socket cherry red, you can melt into the aluminum. You want it hot enough to easily melt the rubber but not hot enough to melt aluminum. Buuuuut, the hotter the better, you have to do it in one shot because you'll just make a mess of things if you don't. WEAR WELDING GLOVES! The heat will travel up the extension and burn the snot out of you if you're not careful.