kyleb0587

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.

chayes627

I had that same exact problem, same cylinder, that plug was hand tight and I did them myself so I know they were tight. . I didn't do a compression test but when I re[placed the plug it ran like a champ.

GDI Tech

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!

techrep

iTrader: (1)

what 4.6 issues ??

GDI Tech

Just the spark plugs breaking off in the hole. 5.4 far more common than the 4.6. Always keep the extractor handy in my box.

techrep

iTrader: (1)

never heard of a broken spark plug problem with the 4.6... it's a one piece plug.

PerryB

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.

techrep

iTrader: (1)

Agree...never know if the plug has a hair line crack or not after a drop..

Aeromech

Change your plugs at 60K miles and be happy

corey_lax

I've changed mine twice and I am still not happy. What is you secret??? haha