Car recently developed a miss and eventually threw this CEL. Info on the car: Replacing the coil pack on cylinder 2 did not resolve the issue. I pulled the plug. The plug was fouled with significant carbon buildup. There was oil on the spark plug threads but no oil visible on the tip or electrode. After replacing the plug the car ran normally. Today I removed the other 7 plugs. All 7 had the same issues with oil on the plug threads to varying degrees. There is also a lot of carbon buildup on the piston crown visible through the plug well. A couple cylinders aren't that bad but the others are pretty caked up with it. The car does not produce any obvious smoke to the eye. It doesn't consume oil either. The oil on the plug threads is a mystery to me. It doesn't appear to be leaking down the well from above. If the rings were shot I would expect the car to be smoking. And all the carbon buildup, also a bit puzzling, makes me wonder if it's running rich. Thoughts?