GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Corvette 🢒 Engine 🢒 Engine Controls - 5.7L 🢒 Detonation/Spark Knock

Detonation/Spark Knock

Checks

Action

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

Preliminary Checks
    • Refer to Important Preliminary Checks Before Starting in Symptoms .
    • Search for bulletins.
    • Inspect the PCM grounds for being clean, tight, and in their proper locations. Refer to Engine Controls Schematics .
    • If the scan tool readings are normal--refer to supporting text of the Powertrain On-Board Diagnostic OBD System Check-- and there are no engine mechanical faults, fill the fuel tanks with a known high quality fuel that meets the vehicle's minimum octane requirements. Refer to Fuel System Specifications . Road test the vehicle and re-evaluate the vehicle's performance.

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Test for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Test the items that can cause an engine to run lean (long term fuel trim near 23 percent). For a lean condition, refer to DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 and DTC P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1 .

Ignition System

Inspect the spark plugs for being the proper heat range. Refer to Spark Plug Usage in Engine Electrical.

Engine Cooling System

Test for obvious overheating problems:

    • Low engine coolant-- Refer to Cooling System Draining and Filling 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
    • Inoperative electric cooling fan circuits--Refer to Electric Cooling Fan Diagnosis .

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.
    • 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.
    • Inspect for the following incorrect basic engine parts:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.

Additional Checks
    • Test the park/neutral position (PNP) switch operation. Refer to DTC P0705 Trans Range Switch Circuit or DTC P0706 Trans Range Switch Performance .
    • Test the transmission torque converter clutch (TCC) for proper operation. Applying the TCC too soon can cause the engine to spark knock. Refer to Torque Converter Diagnosis in Automatic Transmission-4L60 E.