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International Automotive Technicians Network
Re: '13 Mazda 3 with constant P0303, cannot feel misfire
Posted to Technical Discussion Forum on 8/20/2019

I'm with Ray on this one,oil ash deposits are clearly visible on #3 plug. What does the internal of the engine look like? You may have weak oil control rings or the drain back ports in the piston plugged. Neither of those conditions will show up in compression... Login to read more.