Hello. 2004 F150 5.4L the plugs I took out are longer Motocraft while the new ones are shorter. Both types are listed for the vehicle so not sure what the difference is. I mean I don't mind going with the shorter ones but wouldn't you want the spark to be occurring at the proper spot and both of them make that happen at different locations inside the cylinder head.


Also curious your thoughts on the removed plug if they look worn out if there's any kind of weird symptoms it looks pretty worn out to me.


Thanks

 

The short plugs are for the 2 valve engine. You have a 3 valve. They won't even screw in, they have different thread sizes. The long plugs are 16mm, the short ones are 14mm. The only 2004 F150 that had a 2 valve 5.4 is the Heritage model - old 97-03 body style. The correct Motorcraft plug is the SP546. Make sure you coat the ground barrel below the tapered seat with high temperature nickel antiseize, but don't get any on the ground electrode bridge or the tip.

 

Where do you get the nickel stuff? Like the old plugs had that it was sort of silvery I have some copper stuff but I don't suppose that would work.

That's curious that they would even sell me that at O'Reilly's if it's a three valve I'm glad you said something. I knew something was up with the different length. Now I'm curious about the coils. Not sure how accurate Amazon stuff is for a 2004 5.4. I know they're not the bent coils but I wonder what coils are actually the right ones then. This engine's got a hesitation when moderately accelerating and then I think it works through it I think it's probably a coil or maybe multiple ones but I just decided to go through and replace everything since I don't know the motor on this very well I've only had it 10,000 miles.

What do you think on the spark plugs I mean I seen some pretty ugly pictures these don't look that bad but they're pretty worn on the tips.

 

I tried 16mm wouldn't work but 9/16ths did. I screwed around with it after cleaning it out and everything with 16, 15, 14... So deep in there I couldn't tell if it was sitting on top of it cuz it was too small or on the outside and too big. Even the spark plug socket comparable the 16 in SAE wouldn't work but then I used the harbor freight colored 9/16 five point and it turned right out slipped right over it took about 15 seconds to get it out after 20 minutes of screwing around so frustrating. So have no idea why it's supposed to be 16 in the 9/16 is the only thing that fit LOL... Thought I was going crazy it's like the first time I mean how hard could it have to be it's just crazy this truck has been the total pain since I got it. I really miss like an F-350 I'll never get an F-150 again I don't think my sister has a 2016 and it's giving her nothing but problems.

 

I was talking about thread size, not hex size. Coils are DG511, use Motorcraft, Denso, or Delphi. Use dielectric grease in the coil boots, don't overdo it.

https://www.rockauto.com/en/moreinfo...pt=7060&jsn=21

https://www.rockauto.com/en/moreinfo...7212&jsn=10478

 

Well I was able to get all eight plugs out without one breaking. Six of the eight were the old style I think they're SP515s... Two were the new style SP546 and they had no damage and looked really clean. The other ones might have even been the original although there was some anti-seize on some of them so maybe some were replaced. I don't know who wouldn't just replace all the plugs especially knowing there was a new style and the old style was susceptible to problems.

To anybody wondering from what I can tell besides having an h instead of a k on the side of the spark plug like the third letter is an h the old style plugs are not welded at the bottom the little u-shaped end, where the new ones are perhaps this prevents them from breaking apart like the one I'm going to show you in the picture.

But with new coils and plugs the engine is so smooth it just idles so smooth and quiet! No more Miss and the mileage improved by about 25% from what I can tell so far with just about 40 miles on it since. Never threw a code that I could see with a $300 code reader but I'm sure the data would have told me which one had the bad plug. Pictured is the bad plug the bottom of its blown out and it appears luckily that it went out the exhaust or burned up.

I sprayed that penetrating hot stuff I can't remember the name of it in there and then I blew out each of the spark plug chambers with compressed air before removing them. Each one I put about 25% of my strength into it with the hand not the body or breaker bar. Only one I had to put a little extra on and it was the one in the very back on the driver's side. Once it broke they came out almost by hand with very few turns with a wrench so I guess I got pretty lucky.

See a picture of the spark plug that blew out.

 

Yes sir did you get lucky. A lot of folks have been downright foiled by that two piece design.

 

OEM in my '07 was SP507 plugs, I put SP546 plugs in @ about 67,555 miles in July 2019, running smooth as silk here in September 2021 @ maybe 6,5xx miles later.

I have a new set of SP515 plugs I had bought for it, but they were superceded before I did the change.