Detonation/Spark Knock. Cadillac CTS 2004

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2004 🢒 CTS 🢒 Engine 🢒 Engine Mechanical - 3.6L (LY7) 🢒 Detonation/Spark Knock

Inspection

Action

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

Preliminary

•	Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls .

•

Inspect the engine control system grounds for being clean, tight, and in the correct locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Ensure the resistance between the engine control module (ECM) housing and the battery negative cable is less than 0.5 ohms.

•	Verify that the ECM and ECM bracket fasteners are at the correct torque.

•	If the scan tool readings are normal and there are not any engine mechanical faults, fill the fuel tank with a known high quality fuel that meets the vehicle's minimum octane requirements. Road test the vehicle and re-evaluate the vehicle's performance.

Fuel System

•	Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .

•	Test for a restricted fuel filter. Refer to Fuel System Diagnosis .

•	Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

•	Test the fuel injectors. Refer to Fuel Injector Solenoid Coil Test .

•	Test the items that can cause an engine to run lean. For a lean condition, refer to DTC P2177 or P2179 and DTC P2187 or P2189

Sensor/System

Use a scan tool to monitor the knock sensor (KS) system. Refer to Knock Sensor (KS) System Description .

Ignition System

Ensure that the spark plugs are the correct heat range. Refer to Ignition System Specifications .

Engine Cooling System

Test for obvious overheating conditions. Test or inspect for the following conditions:

•	Low engine coolant level

•	Incorrect engine coolant

•	Restricted air flow to the radiator or restricted coolant flow through the radiator

•	Engine coolant leaks

Refer to the following procedures in Engine Cooling:

-	Cooling System Draining and Filling

-	Engine Overheating

Engine Mechanical

•	Inspect for the following engine mechanical conditions:

-	Excessive oil in combustion chambers and for leaking valve seals.

-	High cylinder compression.

-	Incorrect camshaft timing.

-	Excessive carbon buildup in the combustion chambers--Clean the chambers using top engine cleaner. Follow the instructions on the can.

-	For more information, refer to the following procedures in Engine Mechanical-3.6L (LY7):

•	Oil Consumption Diagnosis

•	Engine Compression Test

•	Camshaft Timing Drive Chain Alignment Diagram

•	Setting Camshaft Timing

•	Symptoms - Engine Mechanical

•	Inspect the following components for incorrect basic engine parts:

Camshafts

-	Cylinder heads

-	Pistons, connecting rods or bearings.

-	Refer to the following procedures in Engine Mechanical-3.6L (LY7):

•	Camshaft Timing Drive Components Cleaning and Inspection

•	Camshaft Cleaning and Inspection

•	Cylinder Head Cleaning and Inspection

•	Piston, Connecting Rod, and Bearing Cleaning and Inspection

Additional

Test the transmission torque converter clutch (TCC) for the correct operation. Applying the TCC too soon can cause the engine to spark knock. Refer to Torque Converter Diagnosis in Automatic Transmission-5L40-E.