GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 CTS 🢒 Engine 🢒 Engine Mechanical - 5.7L 🢒 Detonation/Spark Knock

Detonation/Spark Knock

Inspection/Tests

Action

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

Preliminary Inspections
    • Refer to Important Preliminary Inspections Before Beginning in Symptoms - Engine Controls .
    • Search for bulletins.
    • Verify that the powertrain control module (PCM) grounds are 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
    • Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect the fuel injectors. Refer to Fuel Injector Solenoid Coil Test .
    • Inspect for the following conditions that may cause the engine to run lean:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

       - 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.
       - 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 .
       - Manifold absolute pressure (MAP) sensor operation--Refer to DTC P0106 .
       - Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
       - Vacuum hoses that are split, kinked, or improperly connected

Ignition System

Verify that the spark plugs are of the proper heat range. Refer to Spark Plug Inspection .

Engine Cooling System

Inspect for obvious overheating problems:

    • Low engine coolant--Refer to Loss of Coolant in Engine Cooling for the type and amount of engine coolant to be used.
    • Restricted air flow to the radiator or restricted coolant flow through the radiator.
    • Proper tension on the drive belts--Refer to Drive Belt Tensioner Diagnosis .
    • Inoperative cooling fan--Refer to Cooling Fan Inoperative .

Engine Mechanical

Inspect for the following engine mechanical problems:

    • Excessive oil in combustion chamber--Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical.
    • Incorrect cylinder compression--Refer to Engine Compression Test Engine Mechanical.
    • Combustion chambers for excessive carbon buildup--Clean the combustion chamber by using top engine cleaner. Follow the instructions on the can.
    • Inspect for incorrect, worn or damaged basic engine parts. Inspect the following:
       - The camshaft--Refer to Crankshaft and Bearing 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 Bearing Cleaning and Inspection in Engine Mechanical.
    • Refer to Symptoms - Engine Mechanical in Engine Mechanical.