Chances are that the cam cover gasket is leaking and the spark plug holes are filling up with oil. If you did not soak up the oil with cotton balls before you removed the plugs, the oil simply ran down the plug hole into the cylinder. No biggie.
Replace the cam cover gasket. I can send you detailed instructions if you are doing it yourself. The oil can and will break down the plug wires. You can try cleaning them with waterless hand cleaner but you might need to replace them. Hot oil on the insulation will cause misfires, hard starting, and poor running.
Check to be sure you have good spark by pulling the plug wires off the coils. Mark the wires and coil towers so you reattach the in the right order. Have someone crank the engine and look for blue spark between the coil towers.
Good luck and let us know. :)
Tuesday, April 24th, 2007 AT 10:27 AM