So I have an 04 Mountaineer with an 4.6 and it wasn't firing on cylinders 1 and 6. So I pulled the plugs on 1 and 6 and noticed they are both smashed closed from contact with the piston I assume. What could cause this, jumped timing, extremely worn rod bearing causing the piston travel to become to high in the bore? I just bought this vehicle under the assumption that it would need a motor replacement because it was knocking. I took off the valve covers to check the timing chain guides, things looked OK, I replaced everything and fired it up and it didn't knock. Now it wasn't firing on all cylinders, this led me to pull the plugs and find 1 and 6 plugs damaged. Any ideas what's going on???

 

Well, since you state you just bought the truck - I take it you weren't the one who put the plugs that got smashed in to it? If so, are you sure the plugs that got smashed were the CORRECT pugs for the vehicle?

In diagnosing problems I've seen mechanics pick up and use any plug that would fit (smaller Mom & Pop garages typically end up with drawers of used, but OK, parts to save for another time, just in case).

 

These were the original spark plugs (never been changed). All eight plugs are the same type, and they are the exact same length as the new ones I replaced them with (measured with a micrometer). I know it doesn't make any sense, but whatever the situation was we have almost 1K miles on it and the compression is perfect and it runs and drives flawlessly (not even any lifter noise on cold starts).

 

#1, I'm happy as a pig in mud for ya that you have a good-runnin' motor from one that you thought was gonna be replaced. That's awesome!

#2, I, and probably many others, have been toying with a myriad of theories of what could have happened, but it hit me that, without seeing close-up pictures of those plugs I both don't have a great clue as to just how 'smashed' is smashed, nor what could have caused it.

 

Detonation perhaps.

I have seen people do stuff like this at auctions to get the vehicles cheap. Make them run poorly by swapping plug wires or maybe wreck a couple of plugs if it has COP's.

Hard to say really. Drive it till it blows

 

This.
There's no way possible for a stock modular spark plug to be hit by the piston-the valves and combustion chamber are lower in the cylinder than the spark plug.
JL

 

I posted this in the first thread you started by the same title;
Do the tune-up in a bottle technique. First get some spark plug gaskets for your #1 and #6 spark plugs so they won't go in quite so far. Start the engine and once it's up to operating temp. SLOWLY run about a pint of water into it through the power brake vacuum hose. This will blow the carbon off the pistons and then you may have a nice truck that will not need an engine right away. Good luck with it and let us know your results.

 

Is there a shiny surface on the bottom of the electrode that would indicate "contact" or are the plugs deformed from preignition/detonation? I had one like that on my '99 4.6l but not due to contact. There is a tool called See Snake made by Grainger; the fiber optic is supposed to fit inside spark plug holes to view piston condition. Coupla hundred bucks, though.

 

Hey Curt---that See Snake is actually an imported tool made by Rigid Tools---they of the pipe wrench and tools fame! Great tool for a lot of things, available much MUCH cheaper at many many places first thought being FleaBay. I have the Milwaukee version purchased for about $110 nearly new.

Generically these things are nothing more than bore scopes or now called inspection cameras and there are hundreds of such tools available these days. Some are sorta cheap and almost disposable, others quite well made and intended for daily use.

They do have a limit on the size bores they'll fit into---my Milwaukee needs at least 3/4" or 19mm---should check this first.

Sorry I don't have any knowledge of the damaged plug base---sounds troubling if its caused by the pistons though.<!-- / message -->

 

You're right, my bust. The tool is manufactured by Rigid; our local vendor is Grainger. As you said, the buyer should check the diameter of the tool before buying.

Thanks for catch my mistake.