GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Geo 🢒 1996 🢒 Metro 🢒 Engine 🢒 Engine Controls - 1.3L 🢒 Detonation/Spark Knock

Checks

Action

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

Preliminary Checks
    • Refer to Symptoms .
    • Road test the vehicle in order to determine the severity of the condition.

Cooling System Checks
    • Check for any obvious overheating problems.
    • Check for a low engine coolant level.
    • Check for a loose water pump belt.
    • Check for restricted air flow or restricted coolant flow through the radiator.
    • Check for a faulty or incorrect thermostat.
    • Check for the correct coolant solution. The solution should be a 50/50 mix of anti-freeze and water.

Sensor Check

Check for an Engine Coolant Temperature (ECT) sensor that has a shifted value. Refer to Temperature Versus Resistance .

Fuel System Checks
    • Determine whether lean fueling is causing the condition. Drive the vehicle at the speed of the complaint. Monitor the Fuel Trim value while listening for engine noise. Long Term Fuel Trim values will be greater than 20% if a lean fueling condition is present. Refer to DTC P0171 Fuel Trim System Lean Diagnostic Aids.
    • Check for the correct fuel pressure. Refer to Fuel System Diagnosis .
    • Check for inferior quality fuel and the correct octane rating. Refer to Fuel System Specifications . Drain and fill the fuel system with a known high quality fuel that meets the vehicle's minimum octane requirements. Road test the vehicle and re-evaluate vehicle performance.

Ignition System Checks
    • Check the spark plugs for the proper heat range and the correct gap.
    • Check the ignition timing. Refer to Ignition Timing Adjustment .

Engine Mechanical Checks
    • Check for carbon buildup. Remove the carbon with a top engine cleaner. Follow the instructions supplied by the product manufacturer.
    • Check for the use of the wrong camshaft, cylinder head, piston(s), or other incorrect engine part. Refer to Engine Mechanical.
    • Check for excessive oil entering the combustion chamber.

Additional Checks
    • Check for the proper operation of the EGR valve. Refer to Exhaust Gas Recirculation (EGR) System Description .
    • Check for the proper operation of the air induction system.
    • Check the Service Bulletins for any updates.