When your 2024 Subaru Forester displays the P0304 code, the engine control module has detected recurring misfires in cylinder 4. Understanding Subaru's horizontally-opposed boxer engine design enables targeted diagnosis for this compact SUV's combustion problem.
Understanding P0304 in the 2024 Forester
The 2024 Forester features the 2.5L FB25 boxer four-cylinder producing 182 horsepower. Subaru's horizontally-opposed configuration positions cylinder 4 at the rear of the left (driver's) bank. This unique engine layout affects accessibility and service approach compared to conventional inline designs.
Boxer Engine Misfire Causes
The flat-four boxer places cylinders horizontally opposite each other. Spark plugs mount sideways rather than vertically. Standard misfire causes apply—ignition coil degradation, spark plug electrode wear, and fuel injector issues—but the boxer's unique geometry affects how components are accessed and serviced.
Diagnostic Methodology
Retrieve all codes and analyze freeze frame data showing conditions when misfires occurred. Locate cylinder 4 on the left bank, rear position. Access may require working around the inner fender area. Test ignition coil output and spark plug condition. Verify fuel injector operation.
Repair Solutions
Install Subaru-specified spark plugs at correct gap and torque specifications. Clean spark plug wells before removal to prevent debris entry. Replace ignition coils showing degraded output. Address fuel system concerns as identified.