I have a 2004 Nissan altima 2.5l in the shop. and had a misfire code i pulled all plugs and no 2 and 4 had a closed gap. i ask the customer if a tune up had been done any time and they replied no ,, so it is all oem equipment. so how do i explain the spark plug messing up like that. i threw as new set of ngk’s in it and now it is coming back with the same problem
The only explanation is that something inside the cylinder caused the spark plugs to do that. I would recommend to check compression. And check for timing belt tensioner failure. If the timing was able to fluctuate, it could allow the piston to hit the plug.