Detonation/Spark Knock/Pings
DETONATION/SPARK KNOCKDefinition: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening.
PRELIMINARY CHECKS
^ Perform the careful/physical visual checks as described at start of "Symptoms".
^ Make sure the customer has an actual problem.
^ Remove air filter and check air filter for dirt, or for being plugged, replace as necessary.
^ CHECK: PCV system for proper operation by placing finger over inlet hole in valve end several times with the engine idling. Valve should snap back. If not, check PCV hose for blockage or deterioration and replace if necessary. If PCV still fails this test, replace it with the correct part number PCV valve.
ADDITIONAL CHECKS
^ CHECK: EGR operation. Refer to "Exhaust Gas Recirculation (EGR) System,"
^ CHECK: For proper transmission shift points.
^ CHECK: Torque Converter Clutch (TCC) operation. Use CHART C-8.
^ CHECK: For correct PROM or ECM (see Service Bulletins).
COOLING SYSTEM
^ CHECK: For obvious over heating problems.
^ CHECK: Low engine coolant.
^ CHECK: Restricted air flow to radiator, or restricted water flow thru radiator.
^ CHECK: Faulty or incorrect thermostat.
^ CHECK: Correct coolant solution - should be a 50/50 mix of anti-freeze coolant (or equivalent) and water.
SENSOR
^ CHECK: Engine Coolant Temperature (ECT) sensor, which has shifted in value.
Compare ECT resistance to the "Diagnostic Aids" chart in DTC 15 chart.
FUEL SYSTEM
NOTICE: To determine if the condition is caused by a rich or lean system, the vehicle should be driven at the speed of the complaint. Monitoring LT fuel trim will help identify the problem. Lean - LT fuel trim greater than 150. Refer to "Diagnostic Aids" in DTC 44.
Rich - LT fuel trim less than 115. Refer to "Diagnostic Aids" in DTC 45.
^ CHECK: Fuel pressure
^ CHECK: For poor fuel quality, proper octane rating.
NOTICE: If scan tool readings are normal ("On-Board Diagnostic System Check") and there are no engine mechanical faults, fill fuel tank with a premium gasoline that has a minimum octane rating of 92 and re-evaluate vehicle performance.
IGNITION SYSTEM
^ CHECK: Ignition timing. See "Vehicle Emission Control Information" label.
^ CHECK: Spark plugs for proper heat range.
^ CHECK: Ignition wires for shorts or faulty insulation.
^ CHECK: For misfiring, crossfiring or cutting out under load. Refer to "Ignition System Check" chart in "Distributor Ignition (DI),"
ENGINE MECHANICAL
^ CHECK: For carbon buildup. Remove carbon with top engine cleaner. Follow instructions on can.
^ CHECK: For incorrect basic engine parts such as cam, heads, pistons, etc.
^ CHECK: For excessive oil entering combustion chamber.