Detonation/Spark Knock/Pings

SYMPTOM DESCRIPTION:
A mild or severe ping, usually worse under acceleration. The engine makes a sharp metallic knock during acceleration, most noticeable under heavy engine loads.


SYSTEM OR COMPONENT TO CHECK

COOLING SYSTEM

CHECK FOR OVERHEATED ENGINE:

- FAN OPERATION: Check fan clutch operation
- AUXILIARY COOLING FAN: Check temperature switch
- COOLANT LEVEL: Low engine coolant level and leaks.
- WATER PUMP: Operation, loose belts
- RADIATOR: Restricted air flow to radiator or restricted coolant flow.
- THERMOSTAT: Faulty or incorrect.
- ENGINE COOLANT: Correct coolant solution - should be a 50/50 mix of anti-freeze/water.


COMPUTER INPUTS/OUTPUTS

CHECK:

- CONTROL UNIT: Damaged wiring, poor connections or defective control unit.
- KNOCK SENSOR: Defective knock sensor or damaged wiring between sensor and control unit.
- OXYGEN SENSOR: Defective or contaminated sensor. False rich indication, excessive lean air/fuel mixture.

Refer to Computers and Control Systems.



FUEL

CHECK:

- LEAN FUEL/AIR MIXTURE: Test fuel pump pressure and volume output. System pressure too low. Check fuel pressure regulator.
- FUEL INJECTOR: Poor injector spray pattern, clogged, or stuck injector.
- FUEL DISTRIBUTOR: Plugged, damaged or defective; mini filter in fuel inlet banjo bolt plugged or restricted.
- FUEL QUALITY: Poor or contaminated fuel, low octane rating.



IGNITION

CHECK:

- SPARK PLUGS: Improper heat range, heavy deposits.
- CONTROL UNIT: Damaged wiring, poor connections or defective control unit.
- CRANKSHAFT POSITION SENSOR: Damaged or improperly installed crankshaft position sensor, damaged missing or severely worn flywheel teeth, accumulation of ferrous metal particles on sensor tip, poor connection, damaged wiring.
- TIMING: Distributor basic adjustment incorrect.
- IGNITION DISTRIBUTOR, CAP, AND ROTOR: Check for cracks, arcing, moisture, rust deposits or high resistance through rotor.

Refer to IGNITION SYSTEMS.