For 1990-2009 cars

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

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

• | Search for bulletins.

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

• | If the scan tool readings are normal, refer to supporting text of the Engine Controls Diagnostic Check. If there are no engine mechanical faults, fill the fuel tank with a known high quality fuel that meets the vehicles minimum octane requirements. Refer to Fuel System Specifications . Road test the vehicle and re-evaluate the vehicles performance.

Fuel System |

• | Check for incorrect fuel pressure. Refer to Fuel System Diagnosis .

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

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

• | Check the items that can cause an engine to run lean long term fuel trim near 24 percent. For a lean condition, refer to DTC P0131 or P0151

Ignition System | Check the spark plugs for being the proper heat range. Refer to Spark Plug Inspection .
Engine Cooling System | Check for obvious overheating problems:

• | Low engine coolant--Refer to Loss of Coolant in Engine Cooling for the type and amount of engine coolant to be used.

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

• | Inoperative cooling fan--Refer to Fan Clutch Diagnosis in Engine Cooling.

Engine Mechanical | Check for the following engine mechanical problems:

• | Excessive oil in combustion chamber--Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical - 8.1L.

• | Low cylinder compression--Refer to Engine Compression Test Engine Mechanical - 8.1L.

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

• | Inspect the following components for incorrect basic engine parts. Refer to the appropriate procedures in Engine Mechanical:

- | Camshaft

- | Cylinder heads

- | Pistons, etc.

Additional Checks | Check the park/neutral position (PNP) switch operation.