Detonation/Spark Knock

Inspection/Tests	Action
DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that changes with throttle opening.
Preliminary Inspections	Refer to Important Preliminary Checks Before starting in Symptoms - Engine Controls . Search for bulletins. Inspect the powertrain control module (PCM) grounds for being clean, tight and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . If there are no engine mechanical faults, fill the fuel tank with a known high quality fuel that meets the vehicles minimum octane requirements. Road test the vehicle and re-evaluate the vehicles performance.
Fuel System	Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Test the fuel injectors. Refer to Fuel Injector Coil Test . Inspect 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) .
Sensor/System	Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Any water intrusion in the heated oxygen sensor (HO2S) connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage in Engine Exhaust. Any vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Any restricted fuel injectors-Refer to Fuel Injector Coil Test . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/Special Tool) . Any vacuum hoses that are split, kinked or improperly connected Inspect for an engine coolant temperature (ECT) sensor that has shifted in value. Refer to Temperature vs Resistance .
Ignition System	In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement Remove spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Verify that the spark plugs are of the correct type. Inspect for proper ignition system output. Refer to Electronic Ignition (EI) System Diagnosis . An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. Determine the cause of the fouling before replacing the spark plugs. Inspect for damaged or misaligned spark plug boots. Inspect the electronic ignition (EI) module for proper ground connection.
Engine Cooling System	Inspect for obvious overheating conditions: Low engine coolant-Refer to Loss of Coolant in Engine Cooling. A faulty thermostat-Refer to Thermostat Diagnosis in Engine Cooling. A restricted air flow to the radiator or restricted coolant flow through the radiator An inoperative electric cooling fan-Refer to Cooling Fan Inoperative (L61) , Cooling Fan Inoperative (LSJ) or Cooling Fan Inoperative (LE5) in Engine Cooling. Proper tension on the drive belts Correct coolant solution should be a 50/50 mix. Refer to Cooling System Description and Operation in Engine Cooling.
Engine Mechanical	Inspect for the following engine mechanical conditions: Excessive oil in combustion chamber or leaking valve seals-Refer to Oil Consumption Diagnosis in Engine Mechanical. High cylinder compression-Refer to Engine Compression Test 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 Inspect for incorrect basic engine parts. Inspect the following components: The camshaft-Refer to Camshaft Cleaning and Inspection in Engine Mechanical. The cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc.-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. Refer to Symptoms - Engine Mechanical in Engine Mechanical.