How many miles on that plug? Do any of the remaining ones look similar?
I speculate coolant leaking past the plug threads due a failing boot and possible plug working itself loose in the threads. Would be a good time to inspect all plugs and boots, replace and re-torque to 24 ft/lbs using anti-seize and dielectric grease according to best practices.
Was the gap closed like that when it came out? If so, either it was installed that way or something hit it. I don’t understand how the threads could be that rusty and still have been screwed into the head. I doubt a coolant leak would have caused that rust, but if water got into the plug well it certainly could have.
I'm with JWA on that. Looks like upper threads were not in the tapered hole for a while....???
Which engine?
How many miles on the plugs?
Others look like?
Which cylinders misfired?
JWA (and others) have some good tutorials (ford-trucks) on the subject of changing plugs, etc....
Yes, the electrode buildup is not uncommon thread condition is not....
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Pac NW and warmer places
1995 E250 EB 5.8 2WD on to a new owner
2006 E350 EB Elect Top 2WD
Some new occuring to me is what brand plug is this one shown? Since the socket is still in place no way to tell. I don't know that'd be significant but I'm curious none the less.
The closed gap is also an interesting thing as well. The OP has yet to update his own thread---hoping that happens at some point.
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