GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 HUMMER 🢒 2007 🢒 H3 🢒 Engine 🢒 Engine Mechanical - 3.7L 🢒 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.
    • Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views 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 performance of the vehicle.

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Test the fuel injectors. Refer to Fuel Injector Diagnosis .
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • 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 .
       - Vacuum leaks
       - Incorrect fuel pressure--Refer to Fuel System Diagnosis .
       - Restricted fuel injectors--Refer to Fuel Injector Diagnosis .
       - Inspect for proper operation of the manifold absolute pressure (MAP) sensor--Refer to Altitude Versus Barometric Pressure .
       - Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
       - Vacuum hoses that are split, kinked, or improperly connected

Sensor/System

Inspect for an engine coolant temperature (ECT) sensor that has shifted in value. Refer to Temperature Versus Resistance .

Ignition System
    • In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures:
       -  Spark Plug Inspection
       -  Spark Plug Replacement
    • Remove spark plugs and inspect for the following:
       - Correct heat range
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
       - Verify that the spark plugs are of the correct type.
    • Inspect for proper secondary ignition voltage output with J 26792 HEI Spark Tester .
    • An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool.
    • If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs.
    • Inspect for damaged or misaligned spark plug boots.

Engine Cooling System

Inspect for obvious overheating problems:

    • Low engine coolant--Refer to Loss of Coolant .
    • Faulty thermostat--Refer to Thermostat Diagnosis .
    • Restricted air flow to the radiator or restricted coolant flow through the radiator.
    • Inoperative cooling fan--Refer to Fan Clutch Diagnosis .
    • Proper tension on the drive belts. Refer to Drive Belt Tensioner Diagnosis .
    • Correct coolant solution should be a 50/50 mix. Refer to Cooling System Description and Operation .

Engine Mechanical

Inspect for the following engine mechanical problems:

    • Excessive oil in combustion chamber--Leaking valve seals. Refer to Oil Consumption Diagnosis .
    • High cylinder compression--Refer to Engine Compression Test .
    • 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, worn, or damaged basic engine parts. Inspect the following:
       - The camshaft--Refer to Camshafts Cleaning and Inspection .
       - The cylinder heads--Refer to Cylinder Head Cleaning and Inspection .
       - The pistons, etc.--Refer to Piston, Connecting Rod, and Bearing Cleaning and Inspection .

Additional Inspections

Inspect the transmission torque converter clutch (TCC) operation. Refer to Symptoms - Automatic Transmission .