12-24-2025, 12:05 PM
I'm a fairly competent DIY mechanic, but I'm stumped by an intermittent engine misfire diagnosis on my 2012 sedan; the check engine light flashes at idle and under light acceleration, with a persistent P0304 code indicating a misfire on cylinder four. I've already swapped the coil pack and spark plug with known good ones from another cylinder, checked for vacuum leaks around that intake runner, and even performed a compression test which came back normal, but the misfire remains and seems to get worse when the engine is fully warmed up. For those who have chased down a similar elusive misfire, what would be your next logical steps? Should I be looking more closely at the fuel injector for that cylinder, testing the wiring harness for an intermittent break, or considering a failing valve lifter or issue with the camshaft position sensor, even though it's not throwing a separate code?