Detonation/Spark Knock

Inspection	Action
DEFINITION: A mild to severe ping which usually occurs worse while under acceleration. The engine makes sharp metallic knocks that change with throttle opening.
Preliminary	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in their proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . If the scan tool readings are normal and there are not any engine mechanical faults, fill the fuel tank with a known high quality fuel that meets the vehicle's minimum octane requirements. Test the vehicle and re-evaluate the vehicle's performance.
Fuel System	Inspect the fuel system. Refer to Fuel System Diagnosis . Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) . Inspect the MAF sensor for proper operation. This can be done by disconnecting the sensor and looking for an improvement in the operation or the loss of the symptom. Another test is to monitor the MAF sensor reading on the scan tool at idle on a warm engine with all of the accessories turned OFF. The reading should be between 5-15 g/s. Refer to Scan Tool Data List . Inspect the engine coolant temperature (ECT) sensor for proper operation or intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Test for a restricted or plugged fuel injector. Refer to Fuel Injector Balance Test with Special Tool . Test the items that can cause an engine to run lean, long term fuel trim near 23 percent. For a lean condition, refer to DTC P0171 or P0174 .
Ignition System	Ensure that the spark plugs are the correct heat range. Refer to Ignition System Specifications .
Engine Cooling System	Test for an overheating condition. Refer to Engine Overheating (LY7) , Engine Overheating (LA3, LY9) or Engine Overheating (LS6) in Engine Cooling.
Engine Mechanical	Inspect for the following engine mechanical problems: Excessive oil in combustion chamber/leaking valve seals-Refer to Oil Consumption Diagnosis in Engine Mechanical. Combustion chambers for excessive carbon buildup-Clean the combustion chamber by using top engine cleaner. Follow the instructions on the can. Incorrect camshaft timing-Refer to Timing Belt Timing Procedure in Engine Mechanical. Inspect the following components for incorrect basic engine parts: Camshafts-Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical. Cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. Pistons, connecting rods or bearings-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical.
Additional	Test the transmission torque converter clutch (TCC) for proper operation. Applying the TCC too soon can cause the engine to spark knock. Refer to Torque Converter Diagnosis Procedure in Automatic Transmission.