Detonation/Spark Knock/Pings

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

PRELIMINARY CHECKS
- Refer to Preliminary Checks. - Important Preliminary Checks
- 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 Diagnostic Charts / Chart A-3. Testing and Inspection
- Transmission 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 Diagnostic Charts / Diagnostic Trouble Code 15 Coolant Sensor Circuit. Testing and Inspection

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 Diagnostic Charts / DTC 44 Oxygen Sensor Circuit (Lean). Testing and Inspection
- Fuel pressure. Refer to Diagnostic Charts / Chart A-6 Fuel System Diagnosis. Testing and Inspection
- 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.
- Technical Service Bulletins for PROM updates.