Car seems to be running strange and breaking up a bit, i pulled the plugs and the inside of the 3rd cylinder from the left is all black inside where as the other 3 are shiny? the spark plug was also very dusty and dark, the plugs are about 3 months old. the others were clean. i did a compression test a while back at the same cylinder was reading much lower than the others but had the car parked over the winter and didnt touch it. could the piston be shot? what could cause the dust and dark powder? sorry im a newb when it comes to this, thanks for any replies!

 

Looks to me like you need to replace the spark plug seals on the valve cover.

 

Can you take a picture that's in focus?

 

A defect that occasionally occurs in spark plugs is a leak between the electrode and the insulator. This allows combustion gases to leak back into the plug boot and, in this case, the spark plug cavity. In older cars that had a wire and boot on every plug the gases would blow the boot off. Try another plug.

 

thanks for the replies,

also a few weeks back the plug shot out of the valve cover?!?!??! i had to pull over and opened the hood and the plug was sitting on the valve cover? put it back in and it ran normally? ill try and take better pictures....

 

ok so you said you did a comp test and that cylinder was lower in psi, i think there is the answer to your question regarding why are your plug in that cylinder dirty
( carbon deposites from blow by oil, maybe piston rings bad, valve seals ect...)

 

You sometimes see spark plugs in the street that have departed the engine the same way. Anyway, that is why the plug and the top of the head looks dirty, the gasket on the plug was leaking since the plug was loose.

The threads may be damaged from someone over torquing the plug in that cylinder in the past. If that is the case the threads can be repaired by a shop. Otherwise, the plug just wasn't installed properly.

None of this has anything to do with the condition of the valves, piston or rings, the things that would cause low compression in that cylinder.

 

The spark plug shot out?!?!? That explains why the hole is black. Make sure the threads aren't damaged in the head and put a new spark plug in there. Once you know things are all tight down there you'll be good to go. That was an important piece of the puzzle you forgot to mention in your first post op.

 

thanks for all the help!!!