I am working on the neighbors 1998 F150 with a 4.6...It was running a little rough so after getting it scanned we found #4 and #7 had a active miss...I changed the plug in #7 just fine...#4 on the other hand is giving me a problem...Apparently it is rusted in place, When I pulled the plug wire off I noticed it had alot of orange rust transfer on the rubber boot, well I couldn't get a plug socket on it so after looking in it with a flashlight I come to realize the inside of the plug has come out and stuck on top of the plug and had to yank it out with a pair of curved needle nose pliers, it had alot of corrosion and rust on it after getting it off the top of the plug. I put the socket and wratchet back on and I cannot break it loose, I am 6'4 and 365 pounds, so I know its not me, I even put a cheater pipe on the 3/8 ratchet and it wouldn't budge...I looked down into it the best I can and I can see alot of rust residue inside the plug hole...The engine was till pretty warm from driving it earlier (I have the burns on my left arm to prove that...) so I sprayed a liberal amount of PB Blaster down into it and I am hoping it would wick it down the threads as it cooled...Anyone had this problem? It is obvious there has been some moisture around the spark plug but I'm not sure how it got in there as the truck dosen't get drove much...

 

What happens with number four on those engines is if you look above the plug hole there is a heater hose and tube connection. That joint can leak and when it does the coolant drips right down onto that #4 plug boot/hole enters the hole and rusts the plug. Its a common problem on the earlier truck 4.6's. If PB blaster doesn't work try some Kroil, I've heard it works even better than PB. Also try removing the plug when cold. Good luck.

 

Good luck. I have the same problem with a 98 4.6. Both 3 and 4 are frozen in place. I ended up twisting the hex part of the plug off from the bottom. So now I can see the outer shell and the tip still sitting in place. I guess I will be removing the head at this point.

 

I've always heard you should NOT remove the plugs unless the engine is cold when the heads are aluminum. There is a chance of bringing the aluminum threads with the plug.

 

I got it fixed but it wasn't fun...