GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Impala 🢒 Engine 🢒 Engine Controls - 3.4L 🢒 Detonation/Spark Knock

Detonation/Spark Knock

Inspection/Test

Action

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

Preliminary
    •  Refer to Intermittent Conditions before beginning.
    •  Search for bulletins.

Fuel System
    •  Test for a low fuel pressure. Refer to Fuel System Pressure Test .
    • Test for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    •  Inspect any items which may cause an engine to run lean. Refer to the Diagnostic Aids for DTC P0171.

Ignition System

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

    • Inspect for the proper ignition voltage output using the following procedure:
        1.  Attach the J 26792 spark tester to engine ground.
        2.  Connect the spark plug end of the spark plug wire to the J 26792 spark tester. Leave the other end of the spark plug wire connected to the coil being tested.
        3.  Connect the spark plug end of the companion spark plug wire to ground.

The companion spark plug wire is the wire attached to the corresponding coil tower.

        4.  Crank the engine while observing the J 26792 spark tester. A crisp blue spark should be observed.
        5.  Repeat the above steps for each coil.
    •  If spark is not present at the coils, inspect for the following conditions:
       -  Check the coils for cracks, carbon tracking or arcing, or a resistance value outside the specified range.

Coil Resistance
5000-8000 ohms

       -  Check the spark plug wires for signs of arcing, cross firing, cracks, carbon tracking, plug boot damage, pinching, improper routing, or a resistance value outside the specified range.

Spark Plug Wire Resistance
1 968 ohms per meter (600 ohms per foot).

    Important: :  Spraying the secondary ignition wires with a light mist of water may help locate an intermittent problem. The ignition voltage will arc to ground when a secondary component is faulty.

       - Check for a faulty ignition module.
       -  Check the ignition system wiring for a loose ignition module feed or ground connection, or damaged system wiring.
    •  Remove the spark plugs and inspect for the following conditions:
       -  Fouling
       -  Cracks
       -  Wear
       -  Improper gap
       -  Burned or damaged electrodes
       -  Improper heat range or reach
    •  If the spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs. Refer to Spark Plug Visual Diagnosis in Engine Electrical.

Engine Cooling System

Inspect for obvious overheating problems:

    •  A low engine coolant level
    •  A restricted air flow to the radiator, or a restricted water flow through the radiator
    •  Any inoperative electric cooling fan circuits
    •  The correct engine coolant solution should be a 50/50 mix. Refer to Coolant Description in Engine Cooling.

Engine Mechanical

Inspect or test for the following conditions:

    • Any excessive oil in the combustion chambers and leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical.
    •  A low cylinder compression. Refer to Engine Compression Test in Engine Mechanical.
    •  Check the combustion chambers for excessive carbon buildup. Clean the chambers using Top engine cleaner. Follow the instructions on can.
    • Inspect the following components for incorrect basic engine parts:
       -  The cylinder heads
       -  The camshaft and the valve train components
       -  The pistons, etc.
       -  Refer to Engine Noise Diagnosis in Engine Mechanical.

Additional
    •  Test for proper EGR system operation. Refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient .
    •  Inspect the Transaxle Internal Mode Switch input with the vehicle in drive and the gear selector in Drive or Overdrive.
    •  Test the torque converter clutch (TCC) operation. The TCC applying too soon can cause the engine to spark knock. Refer to Torque Converter Diagnosis in Automatic Transaxle.
    •  If the scan tool readings are normal and there are no engine mechanical faults, fill the fuel tank with a known quality gasoline that has a minimum octane reading of 87 and re-evaluate the vehicle performance.