The ECM has detected misfires occurring in multiple cylinders or cannot identify which cylinder is misfiring. This is often caused by a systemic problem affecting all cylinders.
Using the correct diagnostic tools helps identify the root cause of P0300 before replacing parts unnecessarily. Always confirm the fault using live data and manufacturer-recommended diagnostic procedures.
On direct-injection four-cylinder engines, P0300 is often linked to carbon buildup on the intake valves rather than a failed ignition component — walnut blasting the valves is a common fix.
EcoBoost engines can trigger P0300 from spark plug fouling caused by oil consumption past worn piston rings — check oil consumption history before replacing ignition parts.
V8 engines with Active Fuel Management (cylinder deactivation) can set P0300 from AFM lifter failure — this is a mechanical fault, not an ignition fault, and needs lifter/camshaft inspection.
N20/N26 engines are known for coil pack failures at higher mileage — inspect all coils even if only one cylinder is misfiring, since neighboring coils often fail shortly after.
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