Detonation/Spark Knock

Checks	Action
DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening.
Preliminary Checks	Refer to Diagnostic System Check - Vehicle . Refer to Symptoms - Engine Controls . Road test the vehicle and determine the severity of the complaint.
Cooling System Checks	Check for any obvious overheating problems. Refer to Engine Overheating . Check for a low engine coolant level. Refer to Loss of Coolant . Check for a loose water pump belt. Check for restricted air flow through the radiator, or a restricted coolant flow. Check for a faulty or incorrect thermostat. Refer to Thermostat Diagnosis . Check for a correct coolant solution. The solution should be a 50/50 mix of anti-freeze and water. Refer to Draining and Filling Cooling System .
Sensor Check	Check for an engine coolant temperature (ECT) sensor that has a shifted value. Refer to Temperature Versus Resistance .
Fuel System Checks	Check to determine if a lean system causes the condition. Drive the vehicle at the speed of the complaint. Monitoring the Fuel Trim will help identify the problem. If the system is lean, the Long Term Fuel Trim will be more than 20 percent. Check the fuel pressure. Refer to Fuel System Diagnosis . Check the fuel injectors. Perform the Fuel Injector Coil Test procedure and the Fuel Injector Balance Test procedure. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) and to Fuel Injector Balance Test with Special Tool . Check for inferior quality fuel and the proper octane rating. 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 vehicle performance.
Ignition System Checks	Check the spark plugs for the correct gap. Refer to Ignition System Specifications . Inspect the spark plugs for excessive deposits that can glow and pre-ignite the air/fuel mixture. Refer to Spark Plug Inspection . Check the spark plugs for the correct type and the correct heat range. Refer to Ignition System Specifications .
Engine Mechanical Checks	Check for carbon buildup. Remove the carbon with a top engine cleaner product. Follow the manufacturer instructions on the container. Check for excessive oil entering the combustion chamber. Refer to Symptoms - Engine Mechanical . Check for incorrect basic engine parts such as the cam, the heads, the pistons, etc.
Additional Checks	Check for a dirty air filter or a restriction in the air induction system. Check for any Service Bulletins or updates.