Detonation/Spark Knock. Oldsmobile Shelby Series 1 1999

For 1990-2009 cars

#### Detonation/Spark Knock

Checks | 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 Checks

• | Refer to Important Preliminary Checks Before Starting in Symptoms .

• | Search for bulletins.

• | Inspect the powertrain control module (PCM) grounds for being clean, tight, and in their proper locations. Refer to Engine Controls Schematics .

• | If the scan tool readings are normal, refer to supporting text of the Powertrain On Board Diagnostic (OBD) System Check . If there are no engine mechanical faults, fill the fuel tanks with a known high quality fuel that meets the vehicle minimum octane requirements. Refer to Fuel System Specifications . Road test the vehicle and reevaluate the vehicle 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 items that can cause an engine to run lean. For a lean condition, refer to DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 and DTC P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1 .

Ignition System | Inspect the spark plugs for being the proper heat range.

Engine Cooling System

Test for obvious overheating problems:

• | Low engine coolant -- Verify the type and amount of engine coolant to be used.

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

• | Inoperative electric cooling fan circuits

Engine Mechanical

Inspect for the following engine mechanical problems:

• | Excessive oil in combustion chamber or leaking valve seals

• | High cylinder compression

• | Combustion chambers for excessive carbon buildup--Clean the combustion chamber by using top engine cleaner. Follow the instructions on the can.

• | Inspect for the following incorrect basic engine parts:

- | Camshaft

- | Cylinder heads

- | Pistons, etc.