This or any oil/coolant deposits. Post up a pic of them. Try keep them in order.
Chances are u will need a new set of plugs to help diagnose.
If it still runs on 5 cylinders with new spark plugs u need to diagnose which cylinder is misfiring by disconnecting one coilpack at a time with the engine running. The one that doesnt change is ur dud cylinder. Chances are though when u pull the spark plugs u will be able to tell which cylinder is faulty.