Detonation/Spark Knock/Pings

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 "Important Preliminary Checks." Testing and Inspection

^ Make sure the customer has an actual problem.

^ Check for fuel injectors. Refer To Fuel Injector Coil Test/Fuel Injector Balance Test Procedure.
Fuel Injector Balance Test

Cooling System Checks

^ Check for obvious overheating problems. Refer to the appropriate service manual.

^ Check for a low engine coolant level.

^ Check for a loose water pump belt.

^ Check for restricted air flow through the radiator, or restricted coolant flow.

^ Check for a faulty or incorrect thermostat.

^ Check for a correct coolant solution. The solution should be a 50/50 mix of antifreeze and water.


Sensor Check

^ Check for an Engine Coolant Temperature (ECT) sensor that has a shift in value. Refer to DTC P0117 or P0118 "Diagnostic Aids." P0117
P0118

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 greater than 20%. Refer to DTC P0171 "Diagnostic Aids." P0171

^ Check the fuel pressure. Refer to "Table A-7B." Table A-7B Fuel System Diagnosis (Fuel Pressure Check)

^ Check for poor fuel quality and proper octane rating. If the scan tool readings are normal and there are no engine mechanical faults, fill the fuel tank with a premium gasoline that has a minimum octane rating of 92 and re-evaluate vehicle performance.

Ignition System Checks

^ Check the spark plugs for their proper heat range and gap. Check the ignition timing.

Engine Mechanical Check

^ Check for carbon buildup. Remove the carbon with a top engine cleaner. Follow the instructions on the can.

^ Check for incorrect basic engine parts such as cam, heads, pistons, etc. Refer to the appropriate service manual.

^ Check for excessive oil entering the combustion chamber.

Additional Checks

^ Check for the proper operation of the EGR valve.

^ Check for the proper operation of the air cleaner.

^ Check for the proper transmission shift points.

^ Check the Service Bulletins for ECM updates.