Engine Knocking Due to Lean Air/Fuel Mixture

Verify the engine is running a lean mixture by removing and inspecting the spark plugs; a 'clean' or white appearance on the plug electrodes indicates excessive heat from a lean condition. Use a fuel pressure gauge to test the high-pressure fuel system; it must measure 39 PSI (±3 PSI) under load. Check for clogged fuel filters or failing fuel pumps that prevent the system from meeting this pressure requirement at high speeds, causing the engine to run lean and detonate.