Detonation/Spark Knock. GMC Truck Safari

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2002 🢒 Safari - 4WD 🢒 Engine 🢒 Engine Electrical 🢒 Detonation/Spark Knock

Inspections

Action

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

Preliminary

Verify the customer concern.

Cooling System

•	Inspect for a low engine coolant level.

•	Inspect for the proper tension on the drive belts.

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

•	Inspect for a correct coolant mixture.

Refer to Symptoms - Engine Cooling in Engine Cooling.

•	Inspect for a faulty thermostat. Refer to Thermostat Diagnosis in Engine Cooling.

Sensor

Inspect for an engine coolant temperature (ECT) sensor that has a shift in value. Refer to Temperature Versus Resistance .

Fuel System

•	Inspect for a poor fuel quality and a proper octane rating. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

•	If the fuel trim readings are normal and there are no engine mechanical concerns, then fill the fuel tank with a known good fuel and re-evaluate the vehicle performance.

Ignition System

•	Inspect the spark plugs for their proper heat range and gap. Refer to Spark Plug Inspection .

•	Inspect the ignition timing. Refer Distributor Ignition (DI) System Diagnosis .

Engine Mechanical

Inspect the combustion chamber pressure by performing a compression test. Refer to Engine Compression Test in Engine Mechanical.

Additional

•	Inspect the torque converter clutch (TCC) operation. Refer to Symptoms - Automatic Transmission in Automatic Transmission-4L60-E.

•	Inspect the Service Bulletins for calibration updates.