Detonation/Spark Knock. GMC Truck Safari

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1997 🢒 Safari - 2WD 🢒 Engine 🢒 Engine Controls - 4.3L 🢒 Detonation/Spark Knock

Check

Action

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

Preliminary Checks

•	Refer to Important Preliminary Checks .

•	Make sure the customer has an actual problem.

•	Check the Transmission Range (TR) pressure switch assembly operation. Refer to Transmission.

Cooling System Checks

•	Check for an obvious overheating problem. Refer to in Engine Cooling.

•	Check for a low engine coolant level.

•	Check for the proper tension on the drive belts.

•	Check for restricted air flow through the radiator, or restricted coolant flow.

•	Check for a faulty thermostat, refer Engine Cooling.

•	Check for a correct coolant solution. The coolant should be a 50/50 mix of antifreeze and water.

Sensor Check

Check for an Engine Coolant Temperature (ECT) sensor that has a shift in value. Refer to the following items for the Diagnostic Aids:

•	DTC P1115 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage

•	DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage

Fuel System Checks

•	Check if a Lean system causes this condition. Drive the vehicle at the speed of the complaint. Monitoring the Fuel Trim will help identify the problem.

•	If the system is Lean, the Long Term Fuel Trim will be greater than 150. Refer to DTC P0132 HO2S Circuit High Voltage Sensor 1 for the Diagnostic Aids. Refer to DTC P0138 HO2S Circuit High Voltage Sensor 2 for the Diagnostic Aids.

•	Check the fuel pressure. Refer to Fuel System Pressure Test .

•	Check for a poor fuel quality and a proper octane rating.

•	If the scan tool readings are normal and there are no engine mechanical faults, fill the fuel tank with a premium gasoline that has a minimum octane rating of 92. Re-evaluate the vehicle's performance.

Ignition System Checks

•	Check the spark plugs for their proper heat range and gap.

•	Check the Knock Sensor (KS) system operation. Refer to Knock Sensor (KS) System Diagnosis (Overview) .

•	Check the ignition timing. Refer to Enhanced Ignition System Diagnosis (Overview) .

Engine Mechanical Checks

•	Check for carbon build up. Remove the carbon with a top engine cleaner. Follow the instructions on the can.

•	Check the combustion chamber pressure by performing a compression test. Refer to Engine Mechanical.

Additional Checks

•	Check for the proper operation of the EGR Valve. Refer to Exhaust Gas Recirculation (EGR) System Diagnosis .

•	Check for the proper operation of the Air Intake system. Refer to Air Induction System (Overview) .

•	Check for the proper operation of the transmission shift points. Refer to the Transmission Controls section.

•	Check the Torque Converter Clutch (TCC) operation. Refer to Automatic Transmission.

•	Check the Service Bulletins for PROM updates.