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
|
| • | Search for service bulletins. |
|
Fuel System
|
| • | Check items that can cause an engine to run lean--Long Term
FT significantly in the positive range. Refer to Diagnostic Aids for
DTC P0171
. |
|
Ignition System
|
| • | Check the knock sensor (KS) system for no retard timing. |
|
Engine Cooling System
| Check for obvious overheating problems:
| • | Restricted air flow to radiator or restricted water flow through
radiator |
| • | Correct coolant solution should be a 50/50 mix of Dexcool or equivalent
antifreeze coolant and water. |
|
Engine Mechanical
|
| • | Inspect for excessive oil in combustion chamber and leaking valve
seals. Refer to
Oil Leak Diagnosis
in Engine Mechanical. |
| • | Inspect for low cylinder compression. |
| • | Inspect combustion chambers for excessive carbon buildup. Use
ONLY an approved cleaner that is compatible with ethanol fuel in the fuel
tank. |
| • | Inspect the following components for incorrect basic engine parts: |
| • | Refer to the appropriate diagnostic procedures in Engine Mechanical. |
|
Additional Checks
|
- Check the park/neutral position (PNP) switch input with the vehicle
in drive and the gear selector in drive or overdrive.
- Check the torque converter clutch (TCC) operation. The TCC applying
too soon can cause the engine to spark knock. Refer to
Torque Converter Diagnosis
in Transmission Diagnosis.
- If scan tool readings are normal and there are no engine mechanical
malfunctions, fill the fuel tank with a known quality gasoline that has a
minimum octane reading of 87 and re-evaluate vehicle performance.
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