Found the cause of my misfire (Ford 5.4 2-valve plug go pop)

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Apr 15, 2017
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Napa, CA.
Apparently, someone used an insert to fix a blown spark plug previously. Thing is, I'm wondering if they used too short of an insert and the piston took out the end of the spark plug? I'll admit I didn't fix this right and just used another insert and put a new plug and it seemed to stay in, although I still have a pretty much dead miss and the P0303.

Any ideas why the end of the plug would be gone? Was the insert too short or the correct length? The one I put back in was approx. the same as the one that was on the old plug.

Funny thing is except for a poor idle the truck runs great. Good power on the highway and everything.
 

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The "proper" inserts are the lock-n-stitch ones, which perfectly match the contour of the existing taper and feature a locking pin so they can't back out. That's what I had installed on my Expedition, it's the only one officially approved by Ford.

Do you have a borescope? You want to take a peek at that cylinder, because that doesn't look good and there may be other damage.
 
The "proper" inserts are the lock-n-stitch ones, which perfectly match the contour of the existing taper and feature a locking pin so they can't back out. That's what I had installed on my Expedition, it's the only one officially approved by Ford.

Do you have a borescope? You want to take a peek at that cylinder, because that doesn't look good and there may be other damage.
Yeah I plan to acquire a boroscope before going any further. Do you think a lock n stitch or whatever will still work even though the helicoil already failed?
 
Did the coil you used have a tang that had to be broken off or tangless. Call Time-Sert and ask them about oversized inserts. I also have a feeling there is more damage than just the plug.

 
The fake plugs all over eBay can do that, too, but if you replaced and still have a misfire on that cylinder it's not encouraging. Borescope and compression test seem logical places to start .....assuming you can be reasonably sure you can get a good seal with a tester
 
It looks like something physically same in contact with it in the combustion chamber.
 
The fake plugs all over eBay can do that, too, but if you replaced and still have a misfire on that cylinder it's not encouraging. Borescope and compression test seem logical places to start .....assuming you can be reasonably sure you can get a good seal with a tester
Yeah, I don't think the compression tester will seal :'(
 
There's no way we can do that without pulling the head 😌
That kit can be used without pulling the head (my #8 blew out, it was done in the vehicle). However, inspection of the damage definitely needs to be performed and the insert may not work if the hole is already hogged out and then was blown out again.
 
That kit can be used without pulling the head (my #8 blew out, it was done in the vehicle). However, inspection of the damage definitely needs to be performed and the insert may not work if the hole is already hogged out and then was blown out again.
I put almost 200K on my 98 2V 5.4 and never had these issues but I can't imagine doing #8 with the cab still on.

I have 8 thread PI heads now that I went supercharged on the truck, but those were only made in 03 & 04 and are getting impossible to find.
 
I put almost 200K on my 98 2V 5.4 and never had these issues but I can't imagine doing #8 with the cab still on.

I have 8 thread PI heads now that I went supercharged on the truck, but those were only made in 03 & 04 and are getting impossible to find.
Yes, it must have been one hell of a challenge too, because the Expie of course has rear heat and A/C.
 
OK I'm going to get a boroscope tomorrow, inspect the hole and cylinder, and if the rest of the engine looks OK I'm going to jb-weld another heli-coil in there and hope for the best. I may try a shorter spark plug if the insert is too deep :D
 
Do you think you have some variable length connecting rods causing some malice in the combustion palace?
Well, the boroscope didn't work great but it worked enough to look down there and I didn't see anything horrible in the cylinder. I didn't feel like bumping the starter over and over again to see both the valves but the one piece of one valve I saw looked perfectly fine. So I put some JB-Weld High Heat on a Helicoil and using an NGK UR5/2771 spark plug which is shorter I am hoping for the best tomorrow when I test it. I did have to use the shorter spark plug because the correct/normal sized plug I had put in there a few days ago was smashed too (see picture).

I have also attached a comparison of the spark plug I installed today vs the length of spark plug the engine calls for. As you can see the one meant for a small block Chevy protrudes less. So whatever keeps whacking my plugs will hopefully not whack. Lol.

If this doesn't work I'm just gonna get rid of the truck.
 

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I think there is nothing for the plug to seat on and it is going too deep into the combustion chamber.
 
I think there is nothing for the plug to seat on and it is going too deep into the combustion chamber.
Yeah even the short plug seemed to turn and turn and turn. Hope I didn't put it too far in this time. Not like it's ever going to come out now. IDK. I'm about over this stupid truck.
 
Helicoil and JB Weld?

Might as well take out the ad for the sale now.

Nothing short of a new head is going to fix a head that’s been repaired with epoxy, a helicoil, and a plug that “turn and turn and turn.”
 
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