CUSTOMER CONCERN The engine misfires on cylinder 4 with DTC P0304; disconnecting the EGR valve stops the misfire. CAUSE Carbon blocked the individual EGR passages in the intake manifold, concentrating EGR flow into cylinder 4. CORRECTION Remove the intake manifold, clean the individual EGR passages and EGR feed path, reinstall the components, clear P0304, and verify the misfire is eliminated.

CUSTOMER CONCERN The engine misfires with no compression on cylinder 3, no oil registering on the dipstick, cylinder-misfire DTCs and P1286, P128A and P2646. CAUSE Testing confirmed internal engine damage with loss of cylinder compression associated with severe oil consumption. CORRECTION Remove and replace the damaged engine assembly, clear all stored DTCs, and verify compression and normal engine operation.

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.