[PICS] Misfiring cylinder; oil/fuel on broken spark plug; compression?

What's up, guys? It's been a long time since I've posted anything but I've still been lurking, nonetheless.

This is an issue I "fixed" as in I replaced the spark plug but I don't know what the underlying issue is that caused the problem.

I noticed about two weeks ago a really loud knock that was obviously a cylinder and the truck lurching forward while I was driving. I figured it was pre-det or, at worst, a broken rod. We finally got some nice weather today so I decided to see what was going on. After going through all of the spark plugs on my 3RZ-FE, it was the first cylinder that was the issue. Once I pulled the plug, it was covered in oil and fuel I suppose. It didn't really smell like fuel but it was dark like oil. What really blew my mind was when I was able to slide the jacket back and forth.





Everything is fine now that I replaced the plug but what could've caused this. I just replaced all four about three months ago and I haven't been driving it hard or even taking it off-road. Any ideas?

 

Was the center electrode loose and moving or just the ceramic covering loose and moving?

If the center electrode was moving down and making contact with the grounding electrode, just a bad plug. It happens. Kind of rare these days, but it still happens.

G

 

It was the entire threaded sleeve with the grounding electrode that moved as one unit up and down the ceramic portion until it made contact with the center electrode. I hope that a bad plug is all it is. Thanks for the help, Gadget. Knowledgeable, as always.

 

It sounds like you found the culprit and you should be fine. It wasn't a CHAMPION spark plug by any chance was it?

 

denso

 

Ford has a problem with one of their plug designs that this reminded me of.

What happened probably was that the inner section broke from the outer section (It is simply "bonded" during assembly of the plug) and this allowed the entire center of the plug to slip down enough to allow the piston face to contact the tip of the plug. (hence the noise you heard) This bent the grounding tip against the electrode in the center. You are probably fine with a new plug, but to be safe, since you don't know if the other plugs were built in the same lot, I would replace ALL of the plugs.