misfire / spark plug issues

[CaptainKRM]

been having a real bad low and mid range misfire lately on my Explorer swap. Started changing bits and pieces to try an isolate it, figuring the plugs were only six months old, those could not possibly be the problem. oh silly me.

so here are a few pics of the lone offensive plug which caused my misfire. my question is, what in the world would cause this?

[gadget73]

What cylinder(s) is that from? If its from 4 or 8, my vote is on bad valve seals. The rear plugs tend to foul first when the seals are shot. I'm guessing its because the motor tilts back and more oil lays on those seals than elsewhere.

[4door]

separate #7 & 8 wires(they fire one after another, tend to cause a miss) and as GADGET73 wrote above, pull #8 plug and clean it.

[81_TC]

Could be a bad wire too, causing the plug not to fire.

[CaptainKRM]

i am not sure which cylinder number it is (yeah dumb newb). its second plug from the front bumper on the drivers side. no other plugs had any conspicuous marks.

[gadget73]

Thats #6, not the typical oil foul one. Might be a dud wire or plug. It may also be a leaky injector on that cylinder causing it to crap up, though I'd expect it to be more sooty than chunky.

Plugs go 1-4 on the passenger side, 5-8 on the driver's side. 1 and 5 at the front of the motor, 4 and 8 at the rear.