Detonation/Spark Knock

WARNING: This page is about a different car, the 2005 Buick LaCrosse and 2005 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

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	Perform the Diagnostic System Check - Vehicle in Vehicle DTC Information. 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 . Inspect for a restricted fuel system. Refer to Fuel System Diagnosis . Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool , Fuel Injector Balance Test with Tech 2 , or Fuel Injector Coil Test . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With 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. 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. Inspect for an engine coolant temperature (ECT) sensor that has shifted in value. Refer to Temperature vs Resistance . Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2 . For proper operation of the manifold absolute pressure (MAP) sensor-Refer to Manifold Absolute Pressure (MAP) Sensor Diagnosis . For proper operation of the mass air flow (MAF) sensor-Refer to Scan Tool Data Definitions and Scan Tool Data List . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Vacuum hoses that are split, kinked, or improperly connected
Ignition System	Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as water is applied. Inspect the ignition timing. Inspect for proper ignition voltage output with the J 26792 Spark Tester. Remove the spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . Verify that the spark plugs are of the correct type. Refer to Ignition System Specifications . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Ignition System Specifications and Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Inspect the spark plug wires for signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside the specified range. Refer to Ignition System Specifications . Inspect for loose ignition coil grounds.
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 (LY7) in Engine Cooling. Restricted air flow to the radiator or restricted coolant flow through the radiator Inoperative electric cooling fan-Refer to Cooling Fan Inoperative in Engine Cooling. Proper tension on the drive belts-Refer to Drive Belt Tensioner Diagnosis in Engine Mechanical. The 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-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 and Bearings Cleaning and Inspection in Engine Mechanical. The cylinder heads-Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc.-Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Refer to Symptoms - Engine Mechanical in Engine Mechanical.
Additional Inspections	Inspect the park/neutral position (PNP) switch operation. Inspect the transmission torque converter clutch (TCC) operation. The TCC applying too soon can cause the engine to spark knock. Inspect for proper exhaust recirculation (EGR) system operation. Refer to Exhaust Gas Recirculation (EGR) System Description .