P0301 — Cylinder 1 misfire detected

Part of system: Electrical sensing & powertrain inputs

P0301 usually changes how the vehicle drives, shifts, or feels rather than creating an immediate emergency. P0301 flags a combustion miss specifically on cylinder 1, not a random multi-cylinder event. The ECM counts crankshaft acceleration glitches tied to that firing order position, so drivers feel a rhythmic shake at idle and a flat spot under light throttle while fuel trims on the affected bank drift. Start by swapping the cylinder-1 coil and plug with another cylinder to see if the miss follows the parts, then leak-down or relative compression on cylinder 1, and only then chase injector balance or wiring at the coil connector. Oil-flooded plugs after short cold trips and cracked coil boots are frequent winter culprits on coil-on-plug engines. Sort among failed coil-on-plug or cracked boot on cylinder 1, worn, fouled, or wrong-gap spark plug in cylinder 1, and low compression from burned valve or ring wear on cylinder 1 with a methodical road-test mindset. Begin with swap cylinder-1 coil and plug with another cylinder and retest, continue with run relative compression or leak-down focused on cylinder 1, and consider cylinder-1 ignition coil and dielectric grease only after the data still condemns that part.