Spark plug change question

[Mike Poore]

It's time ....should I go ahead and buy/order the coil cover thingeys as well? Where's the best place to get that stuff? What about wires?
Thanks :)

[Breadfan]

For what type of car do you speak of Mike?

[Mike Poore]

For what type of car do you speak of Mike?

Darn, I was hoping to avoid answering that. :o

It's for the 2002 F-150 with 4.6, um, single overhead cam. It just went to 105,000 miles and has never had a tune up and is starting to miss a little.

Back to question #1:)

[Breadfan]

No prob, I had guess, you gave it away by asking about wires...

Is it not coil on plug?

If it is coil on plug, they should be fine unless malfunctioning. Just do the plugs, OEM replacements would be fine, Autolites would work nice.

It probably came stock with platinum tipped plugs, nothing wrong with those.

While changing them with coil on plug check the connectors going into the COPS, and the entire COP unit for signs of damage such as cracks, burns, etc.

If it's not coil on plug, and has the coil packs with wires going to the plugs, then yes you can buy new plug wires. I'd go for a good 8mm set or get an MSD or Ford Racing set, and they'll probably last the rest of the life of the truck.

Also for SOHC motors the way the spark plugs sit and the spark plug wells are, you can get water collecting in them if you wash the engine, or otherwise get water on the motor (big puddle or heavy rain perhaps?) We had this happen on a SOHC 4.6 and it caused a miss and CEL until we found out it was just water causing the miss.

[Mike Poore]

No prob, I had guess, you gave it away by asking about wires...

Is it not coil on plug?

.

Well, yeah, DUH! It's coil on plug, so there's no plug wires.

So I'll go get a set of OEM plugs, swap 'em out, and should be good to go, right? :D

[Breadfan]

Well, yeah, DUH! It's coil on plug, so there's no plug wires.

So I'll go get a set of OEM plugs, swap 'em out, and should be good to go, right? :D

Yep, just inspect the COP's as you take 'em off, and don't forget a bit of anti-sieze on the plug threads. ;)

If you continue to have a miss after that it could be a bad COP, you can track it down by disonnecting them one-by-one, sometimes you can track down the culprit that way.

In theory the COPs should be test-able while running, but that would require the right diagnostic tool or an oscilliscope.

[Mike Poore]

Yep, just inspect the COP's as you take 'em off, and don't forget a bit of anti-sieze on the plug threads. ;)

If you continue to have a miss after that it could be a bad COP, you can track it down by disonnecting them one-by-one, sometimes you can track down the culprit that way.

In theory the COPs should be test-able while running, but that would require the right diagnostic tool or an oscilliscope.

Thanks, Mike. I have a 'scope, but guess a VOM would tell me if there's a short or open in one of 'em. Actually, it's just running a little bit rough, under load, and prolly because the plugs are shot.
So far as the anti-seize stuff goes, I have some great high temp choke tube lube called Break Free. It's some gooey black snot, though, but no problem with aluminium applications. :P

[RF Overlord]

Mike, on the SOHC, be sure to use your compressor to blow out the area around the plugs after you remove the COPS. It's not covered like on the DOHC and a lot of debris builds up down there that you don't want falling into the cylinders.

[Breadfan]

^^^ Good tip regarding the SOHC's


As for the scope, in theory you should be able to use an oscilliscope to see the spark "profile" coming from the COP.

Continuing in theory, there should be a "healthy" spark profile and a not so good-running COP would show itself on the scope.

I know some folks from time to time will get 1 COP that is "marginal" causing a "ghost miss" that only seems to happen anywhere outside of a 20 miles radius of the mechanic's shop. :) It's possible being able to "see" the output you may be able to spot a marginal COP easier.

I think high end diagnostic tools do a very similar thing by graphically displaying the coil output.

Whether or not I ever test this is up in the air, anyway my skills with scopes are very very rusty.

[Mike Poore]

Mike, on the SOHC, be sure to use your compressor to blow out the area around the plugs after you remove the COPS. It's not covered like on the DOHC and a lot of debris builds up down there that you don't want falling into the cylinders.

Thanks, Bob, I was looking for a reason to drag the compressor out to the shed. :D

I picked up the plugs, yesterday, and they go in this morning.

8AM so far, so good. It started and ran OK after the first three on the passenger side. Number 4 is a hoot, though, because they conveniently located it back under the firewall. I got the hold down screw out OK, but the boot doesn't want to come off/out. I just came up for a big mutha pair of channel locks to persuade it.

[Mike Poore]

Good lord! The passenger side was a snap, compared to the driver's side.


Remove air cleaner and attendant plumbing.
Remove the power steering reservoir and mounting bracket
Remove the fuel rail brackets and pull the lines from the injectors and move to the side.
Replace the spark plugs and tighten three of the coil retaining bolts.
Replace the fuel rail into the injectors and tighten the brackets.
Notice the 4th coil retaining bolt is loose and remove the fuel rail assembly.
Tighten the 4th coil retaining bolt and replace the fuel rail & bracket.
While replacing the power steering bracket drop the bolt and socket into the valley of death, between the cylinder heads.
Go to lunch. :censor:

[Breadfan]

Dang you think on a truck they're be plenty of room??

[2,4shofast]

Not easy like you would expect...I changed the plugs on a buddys F150 and it took me about 45 minutes longer than what i would have expected for just plugs!:mad:

[Mike Poore]

It gets worse. One of the injector "O" rings went missing (the one under the firewall, of course) and upon starting there was a gas geyser/flood. I have replacements in hand, and will take the ***** apart again and install the replacement(s), in the morning. Meanwhile, the shed smells to high heaven.

Anyone want to complain why the book calls for a couple of bills to change spark plugs? I've got 7 hrs in the project already, not to mention two trips to town, 1 for the plugs and 1 for the O rings. Anybody want to make a bet on them being the right size? (I got two sizes, just to cover the bases)

Still, less than $25 in pieces-parts, and a nice day in the shed, doing what I like.

[ImpalaSlayer]

i never even looked where they were on my 98 4.6 f150

they wernt any where i could see so i gave up looking.

[Mike Poore]

All done, and running better than ever. My dyno shows significant power gain and it's running smooth as silk, with no gas geysers anywhere.

I'd say, an experienced tech could have done this job in about two hrs. Around here, though, it's first time, every time. :D

Thanks guys for your support and help. :)

[BigCars4Ever]

One of my tips is how to clean the plug holes. While the plug is still in I use compressed air to blow as much dirt out as I can. Then I remove the plug. Then I take a long extension and wrap duct tape sticky side out around the fat end ot the extension. Then I push it into the hole and pull it out with the dirt attatched firmly to the tape. Then I remove the tape and repeat. This way all the dirt is removed and almost none of it falls into the cylinder.