A couple of months ago I was making a 3 hour trip for work in my truck (2005 F150 5.4L). Everything was smooth and all of a sudden I noticed a little bit of engine shudder/missing. I played with the throttle and it smoothed out again so I didn't think much about it since I've had this issue before and it was just a failing plug. I thought I would just check/change them when I got back home. A short distance later I notice a more severe shudder and then a sudden metallic sounding chirp coming from the passenger side of the engine bay. Of course I back off completely and the noise goes away. I ease back into the gas and it does it again. So I start to worry and concentrate on just limping it the last leg of the trip. It makes it the rest of the way and I find a mechanic the next day to drop it off with while I'm on my work assignment. After specifically telling them I suspect a plug issue and giving them a full day run diagnostics, the tech tells me after simply test driving it, that it was bad gas. I immediately questioned what diagnostics they did to come to this conclusion and what else they checked. Nothing else was done other than check codes and a test drive. They charged me $30 and sent me on my way. I limped it back home 3 hours, as long as I was at highway speeds and not under load, it ran fine. Even acceleration was fine. Highway speed under load proved to be a challenge though. So I filled it up with 93 octane and parked the truck only using it sparingly for the last 2 months since it's our third vehicle. Last night, I finally decided to check things out. I started pulling plugs on the passenger side and this is what I found on the first cylinder. Then pulled the one in the cylinder behind it to make sure it hadn't done the same. These plugs have less than 20k on them and they are Motorcraft Platinum.

Evidently, the end strap and part of the insulator sleeve broke off and fell down into the cylinder which was causing the metallic chirp that I heard initially. I'm sure there is some damage to the cylinder/cylinder walls, but after replacing the plug, the truck runs as smooth as it ever has (150k miles). I did run a magnetic probe down into the cylinder to make sure no metallic debris was still in there. Pulled it back up several times with some metallic dust collected on the tip. I plan on replacing the other 7 plugs before I do much more driving. I'm hoping that was a fluke, but have no idea what would cause that to happen.

Anyone ever seen anything like this before or have any clues on what would cause this? I'm an electrical engineer by trade and have 20 years of experience working on my own cars, but I'm baffled. It appears the neighboring cylinder's plug is still mechanically sound.

 

That's usually a result of detonation and cheap gas.

 

Or the plug being loose and the cylinder leans out. With it being a 05 you could have a failing injector too.

 

It's strange. I did not notice any detonation prior to the chirping noise I heard. I had filled up with Shell gas probably 70 miles before it happened. Almost always run Shell and never an issue. I replaced injectors last year and it's running fine now. The plug being loose and leaning out is a scenario I could potentially see as the culprit. Like I said, I'll pull the other plugs and replace them asap. Will definitely make double sure of the torque on the plugs.

 

Thats usually caused by blowby --loose plugs .Those hot gases flowing by the plug cuts it like a oxy-acy torch. The black carbon comes all the way up the plug . On the intake it is pulling in oxygen in past the plug making that carbon around plug white hot . Its best to clean carbon out of tip area of plug with carb cleaner That carbon breaks plugs going in or out . Torque all plugs in with a wrench 25 to 28 foot pounds not by feel . It destroys your boots also put new ones in .

 

^^^what he said. Check the rest of the plugs for looseness. Replace all of the coil boots no need for coils the OEM parts are pretty robust. You shouldn't have to replace all of the plugs again. Pull any out that are loose and inspect for similar damage.

 

The big question is, are those the correct plugs that were installed?