I forget the number, but I also had the code pertaining to cylinder 8 misfiring. I don't know what P1316 means, but the generic message for the code pointed towards a bad spark plug. Which would make sense with the misfiring.

The coil is fairly new and looked ok, but when I pulled the sparkplug I didn't feel so good. Oil. The valve cover gaskets was replaced under warranty back in '09.

 

JTIS and codes PDF both free on here both have it. (Or Search).

Basically, too many misfires and likely cat damage if unfixed soon.

Usually the cause is a coil, not a plug.

 

+1 on bad/failing/failed coil (considering the amount of oil on the washer and spark plug threads) with the pic you posted...

 

The same thing just happened to me. Had a P1314 and a P1111. It was the coils. Took it to the dealer and they did the even bank. They said it's best to change the coils and plugs on the entire bank rather than just 1 or 2 cylinders.....not sure if that's true or just a way to get more $$$.