By Dave West
I’ve replaced plugs on quite a few 5.4Ls now (the 4.6L with plug wires is similar)
and once you’ve done a set they really are not as bad as they look. Contrary to
what some people will say, you don’t 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 radiator 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 three 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 AT (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 nut driver 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. Don’t
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.
Set the gap on the new plugs to whatever it says on your emissions decal on the radiator
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. Cross threaded
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 over tighten 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 takes a few hours.