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. |
| • | Refer to Important Preliminary Checks. |
| • | Search for bulletins. |
|
Fuel System
|
| • | Check for incorrect fuel pressure. |
| • | Check items that can cause an engine to run lean (long term fuel
trim significantly in the positive range). Refer to Diagnostic Aids for
DTC P0171 Fuel Trim System Lean
. |
|
Ignition System
| Check the spark plugs for proper heat range.
|
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 GM 1052753
or equivalent antifreeze coolant and water. |
|
Engine Mechanical
|
| • | Excessive oil in combustion chamber-Leaking valve seals.
Refer to Oil Consumption Diagnosis
. |
| • | Combustion chambers for excessive carbon buildup. Clean using
Top engine cleaner. Follow instructions on can. |
| • | For incorrect basic engine parts. Inspect the following: |
|
Additional Checks
|
| • | Check the Transaxle Range Switch input with the vehicle in drive
and the gear selector in drive or overdrive. |
| • | If scan tool readings are normal and there are no engine mechanical
problems, fill the fuel tank with a known quality gasoline that has a minimum
octane reading of 87 and re-evaluate vehicle performance. |
|
