Detonation/Spark Knock/Pings

DEFINITION
Mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening.

PRELIMINARY CHECKS
^ Perform the careful "Visual And Physical Checks" in Preliminary Checks. - Important Preliminary Checks
^ Make sure the customer has an actual problem.
^ Remove Air Cleaner (ACL) and check for dirt, or for being plugged. Replace as necessary.
^ Check PCV valve system for proper operation by placing finger over inlet hole in PCV valve end several times with the engine idling. PCV valve should snap back. If not, check PCV valve hose for blockage or deterioration and replace if necessary. If PCV valve still fails this test, replace it with the correct part number PCV valve.

COOLING SYSTEM
^ Check for obvious overheating malfunctions.
^ Check for low engine coolant.
^ Check for loose water pump belt.
^ Check for restricted air flow to radiator, or restricted water flow through radiator.
^ Check for faulty or incorrect thermostat.
^ Check for correct coolant solution.

SENSOR
Check Engine Coolant Temperature (ECT) Sensor - Using a digital multimeter to measure resistance, compare ECT sensor resistance with ambient temperature on a cold engine.
^ If ECT sensor resistance is greater than or less than ambient air temperature, check for high resistance in ECT sensor circuit or sensor itself. Refer to Engine Coolant Temperature / Specifications for sensor resistance values. Specifications

FUEL SYSTEM

NOTE: To determine if the condition is caused by a rich or lean system, the vehicle should be driven at the speed of the complaint. Monitoring HO2S voltage using Tech 1 scan tool will help identify the problem.
Lean - HO2S voltage below 450 mV
Rich - HO2S voltage above 450 mV

^ Check fuel pressure.
Refer to Chart A-7B Fuel System Pressure Check. Testing and Inspection

Also refer to On-Board Diagnostic System Check. Testing and Inspection

^ Check for poor fuel quality, proper octane rating.

NOTE: If HO2S voltage readings are normal and there are no engine mechanical faults, fill fuel tank with a premium gasoline that has a minimum octane rating of 92 and reevaluate vehicle performance.

IGNITION SYSTEM
^ Check ignition timing. See underhood "Vehicle Emission Control Information" label.
^ Check spark plugs for proper heat range.
^ Check ignition wires for shorts or faulty insulation.
^ Check for misfiring, crossfiring or cutting out under load.

ENGINE MECHANICAL
^ Check for carbon buildup. Remove carbon with top engine cleaner. Follow instructions on can.
^ Check for incorrect basic engine parts such as cam, heads, pistons, etc.
^ Check for excessive oil entering combustion chamber.

ADDITIONAL CHECKS
^ Check EGR system operation, refer to Chart C-7A EGR System Check. Testing and Inspection
^ Check for proper transmission shift points.
^ Check Torque Converter Clutch (TCC) operation. Refer to Chart C-8A Torque Converter Clutch (TCC) Relay System Check. Testing and Inspection
^ Check for correct ECM, see Technical Service Bulletins.