misfire code I pulled all plugs and no 2 and 4 had a closed gap.

QUESTION:

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 

ANSWER:

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.

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