Checks
| Action
|
DEFINITION: A mild to severe ping which 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 how severe the condition
is. |
|
Cooling System Checks
|
| • | Check for any obvious overheating conditions. Refer to
Engine Overheating
in Engine Cooling. |
| • | Check for a low engine coolant level. |
| • | Check for a loose water pump belt. |
| • | Check for restricted airflow or for restricted coolant flow through
the radiator. |
| • | Check for a faulty thermostat or for an incorrect thermostat.
Refer to
Thermostat Diagnosis
in Engine
Cooling. |
| • | Check for the correct coolant solution. The solution should be
a 50/50 mix of coolant and of water. Refer to
Coolant Concentration Testing
in Engine Cooling. |
|
Sensor Check
| Check for an engine coolant temperature (ECT) sensor that
has a shifted value. Refer to
Temperature Versus Resistance
.
|
Fuel System Checks
|
| • | Determine if 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 values of the Long Term Fuel Trim will approach 20 percent
if a lean fueling condition is present. Refer to
DTC P0171 Fuel Trim System Lean
Diagnostic Aids. |
| • | Check for poor quality fuel and for 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's minimum octane
requirements. Road-test the vehicle, and reevaluate vehicle performance. |
|
Ignition System Checks
| Check the spark plugs for the correct heat
range and for the correct gap.
|
Engine Mechanical Checks
|
| • | Check for carbon buildup. Remove the carbon buildup with a top
engine cleaner. Follow the instructions on the container. |
| • | Check for any incorrect basic engine parts such as the cam, such
as heads, such as pistons, etc. |
| • | Check for excessive oil that is entering the combustion chamber.
Repair as necessary. |
|
Additional Checks
|
| • | Check for the correct shifting and for the correct operation of
the transmission. Refer to
Road Test
in Automatic Transmission. |
| • | Check for the correct operation of the air induction system. |
| • | Check the Service Bulletins for any updates or for any information. |
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