Ok guys I know the issues every time someone tries to change spark plugs in the 5.4 3v. I changed all but number #4. All came out easy but #4 isn't the same size socket.. I vacuumed all the dirt out of the head before trying to remove it butIt he 9/16 socket won't grab it. 9/16 worked for the rest. I moved to 5/8 and of course too big. This is crazy. On top of all this, when I reassembl ed the plugs and packs the truck is running like crap. Extremely rough while under load and smooth in idle. Also it sounds like it is arcing or something st highway speed. Please help. 2007 f150 5.4 . 81400 miles

 

You need to dig around in the plug well and chip the crud off the plug hex and dig it out of the space between the hex and head.

 

GLC, thanks for the reply, I thought of that and used a mirror and flashlight to see into the plug area and I can see all the down to the base. I'm almost willing to leave the old plug in but I need to get the truck running right. The check engine light is blinking when going down the road now. It's not blinking a code, just blinking. How can all this happen with just changing plugs. I used autolite plugs, did I go wrong?

 

You SHOULD have used Motorcraft plugs, sorry!

I know, it seems to me that any old plug of the correct heat range should work, but they don't. There's repeated posts about this in the forum.

Regarding the plug that seems too big, I wonder if your socket is not getting onto it straight? If it's tilted, it probably won't slide down.

- Jack

 

Finally got a socket on the #4 with some assistance from a thinning hammer. Some light taps and the socket grabbed. Looks like they rounded it a little during manufacture. Got the automotive plugs out and motocraft in she is purring..... thanks for the feedback all....