Fuel Knock/Combustion Noise

WARNING: This page is about a different variant/trim than selected.

Checks	Action
DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with the throttle opening.
Preliminary Checks	Refer to Symptoms - Engine Controls . Ensure the vehicle has an actual problem. Inspect for smoke associated with the combustion noise. Refer to Fuel System Checks below.
Cooling System Checks	Inspect for obvious overheating problems. Refer to Engine Overheating . Inspect for a low engine coolant level. Inspect for any restricted air flow through the radiator. Refer to Radiator Cleaning . Inspect for a malfunctioning or incorrect thermostat. Inspect for a correct coolant solution. The solution should be a 50/50 mix of anti-freeze and water.
Sensor Inspection	Inspect the engine coolant temperature (ECT) sensor by using the scan tool in order to compare the ECT with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees more or less than the ambient air temperature on a cold engine, check for a high resistance in the coolant sensor circuit or the sensor itself. Turn ON the ignition with the engine OFF. Observe the actual fuel rail pressure (FRP) with a scan tool. The actual FRP should be between 1.1-1.8 MPa. If it is not, inspect for high resistance in the FRP sensor circuits or the FRP sensor. Refer to Circuit Testing and Wiring Repairs . Inspect for an intermittent crankshaft position (CKP) sensor signal. Refer to Testing for Intermittent Conditions and Poor Connections . Inspect the CKP sensor reluctor wheel. Remove the CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement the reluctor wheel retaining bolts are loose.
Fuel System Checks	If excessive smoke is present, check for a stuck open fuel injector by performing the following procedure: Remove the ignition 1 relay. Remove the glow plugs. Refer to Glow Plug Replacement - Bank 1 and Glow Plug Replacement - Bank 2 . IMPORTANT: Do not stand in front of the glow plug holes while cranking the engine. Crank the engine while observing the glow plug holes for fuel spray. Replace the fuel injectors for the cylinders that spray fuel. Check for fuel in the oil and proper oil level. Refer to Fuel in Engine Oil . Inspect for plugged fuel injectors. Refer to Fuel Injector Balance Test with Tech 2 (Manual Transmission) or Fuel Injector Balance Test with Tech 2 (Automatic Transmission) .
Engine Mechanical Checks	Inspect for incorrect basic engine parts such as cam, heads, pistons, etc. If the engine control module (ECM) glow plug control module (GPCM) or a fuel injector has recently been replaced, it may be necessary to confirm the fuel injector flow rate values. Refer to Fuel Injector Flow Rate Programming . Inspect for any excessive oil entering combustion chamber.
Additional Checks	Compare the scan tool data at idle with the scan tool data list. Refer to Scan Tool Data List (Engine Control Module) or Scan Tool Data List (Glow Plug Control Module) .