Not your average destroyed spark plug, need input!
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Junior Member
Joined: Dec 2015
Posts: 2
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Not your average destroyed spark plug, need input!
I decided to have the spark plugs in my 04' F150 changed out around 10k miles ago. My truck was quickly approaching the 100k mark, and I figured it was about time. Generally, this is something that I would do myself. Taking into consideration all of the horror stories I had read about the 5.4 with the spark plugs breaking, I decided to have a shop perform the work. I'm mechanically inclined enough, but would rather not have to fight any extraction issues.
Luckily, everything went smoothly and all eight plugs came out without a problem. The shop did replace one COP, but that was unrelated. Around 5k miles ago I installed 8 new Accel COPs myself. The truck ran smoothly for a while, but eventually developed a miss. The misfire became more problematic to the point where you could feel the truck shake when the miss wold occur. The obvious culprit was the new COPs, or so it seemed. Driving down the road one day the CEL came on and was flashing. Misfire on cyl 8 detected and lean bank 2. I had a different shop check it out and what was discovered has puzzled me ever since. A number of the spark plugs were only "hand tightened" and the number 8 plug was completely destroyed. The shop installed a new plug and the truck has never ran smoother :knocks on wood.
A compression test was performed and the number 8 cylinder was about 25-30 psi below the others, but still within spec. The shop did not see any remnants of the ceramic or metal from the plug. Hopefully it got kicked out without bending the exhaust valve. If you're familiar with the plug design you know that the spark plug forms a U shape on the top. What could have caused this plug and the ceramic to become destroyed?
Any ideas would be much appreciated.
Luckily, everything went smoothly and all eight plugs came out without a problem. The shop did replace one COP, but that was unrelated. Around 5k miles ago I installed 8 new Accel COPs myself. The truck ran smoothly for a while, but eventually developed a miss. The misfire became more problematic to the point where you could feel the truck shake when the miss wold occur. The obvious culprit was the new COPs, or so it seemed. Driving down the road one day the CEL came on and was flashing. Misfire on cyl 8 detected and lean bank 2. I had a different shop check it out and what was discovered has puzzled me ever since. A number of the spark plugs were only "hand tightened" and the number 8 plug was completely destroyed. The shop installed a new plug and the truck has never ran smoother :knocks on wood.
A compression test was performed and the number 8 cylinder was about 25-30 psi below the others, but still within spec. The shop did not see any remnants of the ceramic or metal from the plug. Hopefully it got kicked out without bending the exhaust valve. If you're familiar with the plug design you know that the spark plug forms a U shape on the top. What could have caused this plug and the ceramic to become destroyed?
Any ideas would be much appreciated.
Member
Joined: Dec 2015
Posts: 4
Likes: 2
You would be surprised what can travel through the combustion chamber w/out much damage, and then how something very small sometimes can do a ton of damage. You lucked out. I would never wait 100k miles to change plugs in any 4.6 or 5.4 due to the known issues. Glad it worked out!
5 Year Member
Joined: May 2014
Posts: 4,574
Likes: 970
From: Chico, Ca.
New plugs loosening up is not uncommon in a 5.4 I can't explain the broken plug except maybe it was dropped. With a background in aviation mechanics I don't attempt to save dropped plugs. They get scrapped.
