Oily Sparkplug

[MiXdNuTs]

I have a 1.6L Sentra and after a tuneup the car ran great for a few weeks. Then my gas mileage dropped and I started to loose oil volume and the remaining oil is black and dirty. I opened the hood and the cap for the in the valve cover was about 1" hanging out!
I tried to snap it back in but it wouldn't snap. I looked in and my spark plug had come apart and the top nipple was stuck in the wiring plug. The spark plug was also covered in black engine oil.
I replaced the plug and fixed the wire and the engine runs smoother now,but I am concerend that this may be due to a cross thread or something like that.

Will boths sides of a spark plug get oily when the cylinder is not firing properly? Or is this something much worse? I just can't imagine how oil get around the back side of the spark plug.

[slideways...]

you mean theres oil on the ceramic part? or the electrode part?
if its on the ceramic part, no worry, its just a leaking grommet. a new valve cover gasket set should come with new grommets also. if its on the electrode, it could be a number of things. anything from a blown headgasket to blown piston rings, to bent valves, cracked valve guides, bad plugs, bad plug wires, distributor cap or rotor, you get the idea.

[MiXdNuTs]

It's probably just the gromet then. That makes two seperate issues with the cap (on the ceramic side) of the plug comming off and a leaky gromet. The valve cover seal that I installed actually did not come with gromets.

Since I noticed the problem my car leaks/eats about a quart of oil a week. It couldn't have been all going into the spark plug hole so I am curious where is is getting out. I will have my mechanic look under the car when I get the oil changed.
What is really odd is that like 4 days after an oil change my oil was already dark and dirty....Can't be good for my PCV valve.