Checks 
 | Action 
 | 
DEFINITION: A mild
to severe ping that is usually worse under acceleration. The engine makes
    sharp metallic knocks that change  with throttle opening. 
 | 
Preliminary Checks 
 | 
|     •  | Road test the vehicle in order to determine the severity of the
condition. |  
  
 | 
Cooling System Checks 
 | 
|     •  | Check for any obvious overheating problems. Refer to 
Engine Overheating 
 in Engine Cooling. |  
  
|     •  | Check for a low engine coolant level. Refer to 
Loss of Coolant 
 in Engine Cooling. |  
  
|     •  | Check for a loose water pump belt. |  
  
|     •  | Check for restricted air flow to the engine compartment. |  
  
|     •  | Check for restricted coolant flow through the radiator. |  
  
|     •  | Check for the correct coolant solution. The solution should be
a 50/50 mix of anti-freeze and water. |  
  
 | 
Sensor Check 
 | Check for an engine
coolant temperature (ECT) sensor that has a shifted value.      Refer to 
Temperature Versus Resistance 
. 
 | 
Fuel System Checks 
 | 
|     •  | Determine whether lean fueling is causing the condition. Drive
the vehicle at the speed of the complaint. Monitor the Fuel Trim value while
        listening for engine noise. The long term fuel trim values will be
 approaching        20 percent if a lean fueling condition is present.
Refer to Diagnostic Aids in 
DTC P0171 
and 
DTC P0174 
. |  
  
|     •  | Check for inferior quality fuel and the correct octane rating.
Refer to 
Fuel System Specifications 
.
  Drain and fill the fuel   system with   a known high quality fuel that 
meets   the vehicle minimum octane   requirements.   Road test the vehicle
and  re-evaluate   vehicle performance. |  
  
 | 
Ignition System Checks 
 | Check the
spark plugs for the proper heat range and gap. Refer to 
Ignition System Specifications  
 | 
Engine Mechanical Checks 
 | 
|     •  | Check for carbon buildup. Remove the carbon buildup with top engine
cleaner. Follow the instructions on the container. |  
  
|     •  | Check for incorrect basic engine parts such as the camshaft, heads,
pistons, etc. |  
  
|     •  | Check for an excessive quantity of oil entering the combustion
chamber. Refer to 
Oil Consumption Diagnosis 
  in Engine Mechanical. |  
  
 | 
Additional Checks 
 | 
|     •  | Check for the proper shifting and operation of the transmission. |  
  
|     •  | Check for a dirty air filter or restrictions in the air induction
system. |  
  
|     •  | Check the Service Bulletins for any updates or information. |  
  
 |