I recently picked up an 08 spec v sentra. The car idles roughly with noticeable misfires fairly frequently. I have replaced the spark plugs, found oil on them, and have now replaced the valve cover as well. The engine still idles poorly, with basically no improvement, and what is even more concerning to me is that two of the 4 coil packs still have traces of oil appearing on them. Is this oil possibly coming from the coil packs themselves, I understand that coil packs do have a liquid insulation of some kind? Or do I have a bigger problem?