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Racerguy 03-11-2003 08:28 PM

How to replace your 4.6L & 5.4L spark plugs
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.

dtilden 03-25-2003 08:27 PM

How to replace your 4.6L & 5.4L spark plugs
Changed my 4.6L plugs (in my '00 Econoline) two weeks ago at 74,000 miles. The #5 coil went bad, so I while I was in there... - it took about 4 hours. I had to take the fuel rail loose to get plug #6 out, and left it off for 7 and 8. Knuckle scars are just about healed.

There's just a lot of hardware, hoses & wires to poke an extension through. My tip is to get different length extensions, and maybe some u-joints for your socket set. Plus, a 7mm socket and a 1/4" drive, or an adapter for your 3/8".

Or just be happy that YOU don't have to change the plugs on an Econoline.

Ultramagdan 05-04-2003 08:27 AM

How to replace your 4.6L & 5.4L spark plugs

Originally posted by Racerguy

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.

I removed the front wheels on my truck and lowered it. Made it much easier to reach in change the plugs.

Ratltraps_Fla 05-06-2003 07:05 PM

How to replace your 4.6L & 5.4L spark plugs
I just changed the plugs on my father-in-law's 4.6 (with plug wires). I was lucky to not have any trouble, as it had 170,000 miles with no change. It wasn't as bad as I've heard...but I do have a few suggestions.

1. Take a shop-vac and get any dirt or debris out of the plug area after removing the wires but before removing the plugs. (his had some dirt and a few leaves in some)

2. spray a little penetrating lubricant around the plugs and let them absorb as much as possible while you're working on something else (I chose a cold refreshment)

3. for the back plugs on either side, I found it easier to use a stubby ratchet that swivels at the head

4. also, I rubbed a SMALL amount of dielectric grease on the new plugwire boots so next time I wouldn't burst a vein in my forehead trying to remove them

good luck

rsmith974x4 06-05-2003 09:18 PM

How to replace your 4.6L & 5.4L spark plugs
mine had about 120000 on it no prob w/ seiz but boy the dirt...
and make sure to get wire head seated all the way or it will arc and leave a carbom line down the plug and will miss fire from then on 97 f150 4x4

dgolson 06-23-2003 05:34 AM

How to replace your 4.6L & 5.4L spark plugs
I can understand everyones complaints with changing the plugs in the 4.6/5.4. I used to own a '98 f-150 with the 4.6 and everyone I had talked to said changing the plugs were a nightmare. I beg to differ. It may be a little cramped and tight but they say that patience is a vertue. It can be done in about 45min if you take your time. check with your ford dealer and see what they have to say about plug change times. Mine suggested their book time to be about 2.5 hours. No wonder service prices at the dealer ship cost the customer large. with that said i can't give any more tips on easy of change except to avoid the NGK brand of plugs. they work great for about 20 mins and then foul to the point of no use. a 4.6 will run on 3 cly. not nicly but will run. From trying different plugs I found the Boush +4 gives a nice combination and help the fuel economy issue. As for cop problems I currently have 83000 kms on my 2000 with a 5.4 and the only problem experienced with the ignition is every wiring nightmare. WATER. If you wash under the hood try to get as much moisture out of the plug area. I find a can of compressed air designed to clean computer keyboards works very well, if there is no blow gun avaiable

Racerguy 07-06-2003 01:34 AM

How to replace your 4.6L & 5.4L spark plugs
If you take your truck and get it scanned for codes it will tell you which cylinder is misfiring....if the check engine light is on.
If not you can remove the connectors off the injectors one at a time to figure out whiuch cylinder is dead.

hugepettyfan 07-06-2003 12:41 PM

How to replace your 4.6L & 5.4L spark plugs
#4 is rear hole on passenger side... This is always the first COP to go. Don't bother with plugs unless you are over 100km or 60k mi. #8 is much harder to get at! *Disconnect* battery before you start, main fuse block is really close to your arms when you are buried in there!

hugepettyfan 07-06-2003 12:43 PM

How to replace your 4.6L & 5.4L spark plugs
Almost forgot, check the clamp on the coolant line above the #4 COP... Mine was only finger tight!

Racerguy 07-22-2003 07:21 PM

How to replace your 4.6L & 5.4L spark plugs
Hi Big T and welcome to FTE :)

Good to hear that you got your plugs changed. It's not really as bad as it looks eh? I find that on a van, before I do anything else, I remove the front seats. It makes working on the engine waaay easier and only takes 5 minutes to do.

dwayneh 08-13-2003 02:30 PM

How to replace your 4.6L & 5.4L spark plugs
You covered it very nicely! I just did it on my '97 F150, with the 5.4L Triton. When I first looked at it, I was really intimidated but after doing a little looking around in the Haynes manual I have I just decided to dig in. It took quite a while but the steps you outlined pretty much hit it on the head. I did one other thing, I took the injector rail off completely on both sides. That allowed me to go straight into the spark plug holes directly. I got some gas all over and it took a brief second to pressurize when I was all done but it worked fine. Also, I took my pair of normal car ramps and used an 8 foot 2x12" board in front of the truck. I set the board on the ramps which raised me up enough to lean over onto a blanket which kept me from sustaining too much bodily injury <grin>. I wished I'd have found this forum beforehand, your description would've definitely helped.

Racerguy 08-17-2003 11:54 PM

How to replace your 4.6L & 5.4L spark plugs
Hi Ele0237m :)

Sorry it has taken so long for someone to answer your question. I guess everyone was busy this weekend.

COP means Coil On Plug.
Instead of a remote coil or coils with wires to the spark plugs each spark plug has it's own coil mounted right on top of it.
Have you done anything to your truck to try to figure out the rough idle? Check engine light ever come on?

Racerguy 08-17-2003 11:59 PM

How to replace your 4.6L & 5.4L spark plugs
1 Attachment(s)
Here is an idea what the COPs look like......

Racerguy 09-06-2003 09:08 PM

How to replace your 4.6L & 5.4L spark plugs
Hi Joe and welcome to FTE :)
#7 and 8 are a pain but you managed to do the rest of them so I'm sure you can do those too :)
I use a 7mm swivel (universal joint) socket to remove the COPs but you can use a wrench too or a socket and swivel.
Other than that you just have to be creative with your extensions and swivels etc.

mike_mcd1 09-09-2003 11:24 PM

How to replace your 4.6L & 5.4L spark plugs
Ok guys I did it I changed the spark plugs, but I'm not done. Two of the rubber boots got stuck in the head, so I tried to get them out with a pair of pliers cause of course they were the number 3 & 4 plugs behind the firewall. They both tore. I got them out but need new ones. Did you ever see the warning that says "Remove positive cable off battery". Well now I know why they say that. I hit the load side of the fuse with my rachet and it sparked and blew the main fuse. So tomorrow I go in search of a fuse and two boots. Almost makes me wonder why I didn't just trade it in for a newer model :-huh
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