How did this happen?!

[plumb4u2]

Ok guys so I know enough about cars/trucks to get me in trouble so can anyone explain to me how this happened to this spark plug?

Here’s the story....this is my 98 f150, it is just a work around the house kind of truck if I put 1000 miles a year on it that’s a lot
Last New Years I took it to my buddies mountain cabin and while driving out there going up a mountain “pushing the accelerator “ the truck started bucking and check engine light flashing. I pulled code and it was “cylinder 4 misfire”

Well I’m just now getting to the repair and I bought all new plugs and swapped them yesterday
This picture is the #4 plug which obviously is bent and causing the misfire

Truck is driving perfect now with new plugs but my question is why/how did that plug bend like that?

[Bob Kontak]

Guessing a chunk of carbon broke free from the back of the intake valve.

[rattlsnak]

Usually happens when its being installed....

[flatbutt]

I'd say install error too but then it should have run poorly right away. No? Chunk o' gunk shorting the electrode?

[DanielDudley]

Well, you could look into the hole with a borescope and see if it looks like a gremlin has been hitting the top of your piston with a ball peen hammer. I have seen engines eat small washers and such, but only occasionally do they spit them out and keep running.

I'd go with Bob's analysis and keep driving. A compression test is never out of order.

[plumb4u2]

Well the deal is that I bought this truck about 5 years ago for $2k with no service history except being told “engine was replaced 40k miles ago”
It ran perfectly before that day going up the mountain and is running perfect now after new plug

The truck owes me nothing so if it explodes it will most likely just go to the scrap yard, if I drive this truck 2-3 a month that’s a lot

I guess I’ll just keep on going and hope everything works out

Thanks guys

[ckelly78z]

You got lucky that the plug didn't loosen, and strip the threads like it did in my 04 Mustang 4.6L. I had to fix with a helicoil way down inside the head. Another big problem with the 4.6, and 5.4 motors is actually changing the sparkplugs without bringing some of the aluminum head threads with it when removing old plugs.

[smadsen]

Probably happened on install. Wasn't exposed until the throttle up episode. Pretty hard to close 60 thou gap by accident. Do the open throttle again & then check the plug gap.

[JackDidley]

Loose rod bearing will let the piston come up and hit the plug. Any knocking sounds ?