Detonation/Spark Knock/Pings

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

PRELIMINARY CHECKS
^ Refer to Diagnostic Notes. Initial Inspection and Diagnostic Overview
^ Make sure the customer has an actual problem.
^ If there is spray from only one injector on the TBI unit, there may be a malfunction in the injector assembly, or in the signal to the injector assembly. The malfunction can be isolated, by switching the injector connectors. If the problem remains with the original injector, after switching the connector, the injector is defective. Replace the injector. If the problem moves with the injector connector, the problem is an improper signal in the injector circuits. Refer to "Chart A-3."
^ Trans Range (TR) pressure switch assembly operation.

COOLING SYSTEM
Check:
^ For obvious over heating problems.
^ Low engine coolant.
^ Loose water pump belt
^ Restricted air flow to radiator, or restricted coolant flow.
^ Faulty or incorrect thermostat.
^ Correct coolant solution.

SENSOR
Check:
^ Engine Coolant Temperature (ECT) sensor, which has shifted in value. Refer to DTC 15 Diagnostic Aids.

FUEL SYSTEM
Check:
^ To determine if the condition is caused by a lean system, the vehicle should be driven at the speed of the complaint. Monitoring fuel trim will help identify the problem.
^ Lean - Long term fuel trim greater than 150. Refer to "DTC 44 Diagnostic Aids." Powertrain Controls - ECM/PCM
^ Fuel pressure. Refer to "Chart A-6." Related Tests, Information and Procedures
^ For poor fuel quality and proper octane rating.
^ If scan tool readings are normal 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:
^ Spark plugs for proper heat range and gap.
^ Knock Sensor (KS) system operation.
^ Ignition timing.

ENGINE MECHANICAL
Check:
^ For carbon buildup. Remove carbon with top engine cleaner. Follow instructions on can.
^ For incorrect basic engine parts such as cam, heads, pistons, etc.

ADDITIONAL CHECKS
Check:
^ Proper operation of EGR valve.
^ Proper operation of air intake system.
^ For proper transmission shift points.
^ Torque Converter Clutch (TCC) operation.
^ Service Bulletins for PROM updates.