Could be a bad injector. If the injector is not providing as much fuel to that cylinder the computer see the cylinder when it fire as not providing the same amount of power as the other cylinders, it counts that as a misfire. OInce the computer count x numbers of misfires from that cylinder it shut off the fuel supply to that cylinder and now the cylinder is dead. Resetting the code or shutting off engine just reset misfire counter. You replaced the coil or swap out the coil, but did you swap out or replace the spark plug?

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