[joegr]

Marginal COPs (Coil-On-Plug ignition coils) are a very well known common problem on these cars. I strongly recommend to you that you replace all eight COPs and all eight spark plugs. If you find oil in any of the spark plug wells, then you also need to replace the valve cover gaskets.

(You could just replace the one COP and plug, but I promise you that several more are marginal and just haven't failed completely yet.)