Changed my plugs a couple of weeks ago in my 98 Duratec to hopefully solve hesitation issue and surging. Middle plug TUBE on rear bank (#2) had a smidge of oil at the bottom from a leaking valve cover gasket. Cleaned out before installing new plugs but didn't have the time to change gasket out. If the tube gets more oil in it could this possible cause the plug to ground out? There seems to be a faint popping noise inside valve cover in the same area as the #2 cylinder. Doesn't sound like a valve and it's pitch doesn't change drastically when you accelerate. I'm wondering if the plug could be grounding out.