CUSTOMER CONCERN Engine runs rough for several seconds on the first cold start, coolant level drops over time, and the PCM stores DTCs P0302 and P0316. CAUSE Confirmed failed cylinder head gasket allowing coolant intrusion into a cylinder during cool-down. CORRECTION Remove the cylinder head, replace the failed head gasket, refill and bleed the cooling system, clear DTCs P0302 and P0316, and verify cold-start operation.

CUSTOMER CONCERN Check-engine light is on with a cylinder misfire and fuel-injector circuit fault. CAUSE Confirmed failed fuel injector. Injector resistance specification is 11-18 ohms; the confirmed-fix entry did not document a measured value. CORRECTION Remove and replace the failed fuel injector, clear DTCs, and verify the engine runs without a misfire or check-engine light.

CUSTOMER CONCERN The engine runs very poorly after air-filter service, pings under load, remains in open loop, and stores lean and misfire DTCs. CAUSE Inspection confirmed debris contamination on the mass-airflow sensor element, causing incorrect airflow measurement and the lean misfire. CORRECTION Clean the mass-airflow sensor element and air-filter housing, clear the DTCs, and verify closed-loop operation and normal engine performance.