When your 2021 Honda Ridgeline sets P0302 specifically during acceleration, towing, or other high-load conditions while idling fine, this pattern reveals important diagnostic information. Misfires under load with no idle issues point to specific causes that only manifest when the engine works harder.
Why Misfires Occur Under Load
Under load, the engine draws more air and fuel into the cylinders and creates higher compression pressures. The ignition system must produce a stronger spark to reliably ignite this denser mixture. Components that work adequately at idle may fail under the increased demands of acceleration or towing.
The 3.5L V6 in the Ridgeline makes 280 horsepower, and cylinder 2 is on the passenger side bank. Load-specific misfires in this cylinder indicate weakness in the ignition chain or fuel delivery to that cylinder.
Ignition System Under Stress
Ignition coils that produce borderline spark energy may fire successfully at idle but fail under load. Internal coil degradation reduces spark intensity. The higher cylinder pressure under load requires more voltage to jump the spark plug gap. A weak coil that worked fine yesterday may suddenly cause load misfires as it crosses the failure threshold.
Spark plug gap affects load performance significantly. As plugs wear, the gap widens, requiring more voltage to bridge. A plug with 0.050" gap instead of the specified 0.040" demands substantially more voltage, especially under boost or load. Check and adjust (or replace) plugs if gap is out of specification.
Fuel Delivery Considerations
Under load, the fuel system must deliver more fuel at higher pressure. A partially clogged fuel injector may provide adequate fuel at idle but insufficient fuel under high demand, causing lean misfire. Fuel pressure testing under load can identify weak fuel pumps or regulators.
The VCM Factor
The Ridgeline's VCM (Variable Cylinder Management) can complicate misfire diagnosis. Cylinder 2 is one of the cylinders that VCM can deactivate. Issues with the VCM solenoid or rocker arm mechanism affecting cylinder 2 can cause intermittent misfires, particularly during the transition between VCM modes.
Diagnostic Approach
Given the load-specific nature, diagnosis under load is important. A road test with scan tool monitoring misfire counts while accelerating provides valuable data. If misfires spike during acceleration but disappear at cruise, focus on ignition strength. Swap the coil and plug from cylinder 2 to another cylinder and retest.