I wrote this out for someone else but I figured I'd post it here too. The 4.6L with plug wires is a bit different but similar.
If anyone has any comments or other ideas on how to do the job post them here and maybe we can combine them all and make one good tech article.

It seems that most people on here recommend Motorcraft spark plugs. That is all I will use too. Some people on here have had good luck with other brands and some people have had bad luck. Gimmick type spark plugs seem to usually be a waste of money. Something to remember is that a spark can only jump one gap at a time so having 2, 3, or 4 electrodes doesnt make much sense to me.
Autolite and Motorcraft spark plugs are not the same. The same company that makes Fram filters also makes Autolite plugs. I wont use Fram filters and I wont use Autolite plugs. That is just my opinion though.
Motorcraft plugs can be bought at your local dealer and the prices at the dealer wont always be more than at other places. Ford has been keeping the prices on their common parts in line with the aftermarket in most cases. Apparently most Autozones also carry Motorcraft spark plugs.

Remember just because I'm a moderator here doesn't mean I know everything so feel free to comment

Click on the blue words to see pictures.


I've replaced plugs on quite a few 5.4s now and once you've done a set they really arent as bad as they look.
Contrary to what some people will tell you, you dont have to remove the fuel rails. The Coil On Plug (COP) assemblies will come out past the fuel rail.
I take an old piece of seat foam and put it on top of the rad support to the engine to allow me to lay on it without hurting my tummy
It makes the job way less painful.

Start by removing the cover over the throttle body...the black plastic cover that says 5.4 on it. There are 3 10mm head bolts that hold it on. Next remove the air intake tube from the throttle body to the air filter housing. You loosen the hose clamps at either end of it, disconnect the connector on the IAT (about half way up the air intake hose), the pull out the small hoses that go into the air intake tube near the throttle body.
Next remove the brace from the power steering reservoir to thermostat housing. There are three 8mm or 5/16" head screws that hold it on.
Now you should be able to see the COPs
To remove the COPs you can use a 7mm or 9/32" wrench or nutdriver or socket, extension and ratchet or all of the above.
If you turn the fuel injectors to the side it will give you more room to work with the COPs. Unplug the connector on each COP by pressing the tab in and pulling on the connector. After you're done that just twist and pull the COPs out. A couple of the COPs on the driver's side and #4 on the passenger's side are a bit hard to get at but with some patience they will come out.
After you've removed the COPs take a blow gun and blow out the spark plug holes. Dont be surprised if there is rust and junk in them.
Next you can actually remove the plugs. Use a combination of extensions, swivels (universal joints), sockets and ratchets to get at them. Whatever works best for you is good
On the harder ones to get at I usually use a socket with a 4" extension, then a swivel, then a long extension, then the ratchet.
The plugs are way down in the holes which is why I use the extension then the swivel. The swivel makes it easier to clear the firewall etc.
Set the gap on the new plugs to whatever it says on your emissions decal on the rad support....usually .052-.056".
Apply a small amount of anti-seize to the threads only on the spark plug.
You can use a piece of vacuum hose or fuel hose over the end of the plug to get it started in the hole. Carefully start the plugs in their holes. If you can't get them most of the way in by hand with the hose take a look and see why not. Crossthreaded plug threads are no fun
The plugs are to be tightened to 13 lb-ft. which is just hand tight with a short ratchet.
Don't overtighten them! The threads in the aluminum heads have enough problems as it is.
After that just put everything back together in reverse order.
Apply some dielectric grease to the plug boots as well to help seal them.

I've done enough of these that I can replace the plugs in approximately 45 minutes but don't be surprised if the first time you do it it takes a few hours.