99 Sable 1 cyl not firing

I have a 99 sable that was running rough. I gave it new plugs and wires and air filter and this helped for a short time. It started running rough again so I pulled the plugs to see all were normal except 1. It was soot covered and a little moist. I think I may have valve hanging open. I'm going to have a friend hook up his compression tester to it and see. Would welcome advice on this or other possible causes of these symptoms.:confused:

Hi,

If the "soot" is black and oily, then it is a clear indication of oil consumption and you will need to find out where the oil is coming from -- the pistons and rings, or the valve guides.