Detonation/Spark Knock
Checks
| Action
|
DEFINITION: A mild to severe ping that is usually worse during acceleration.
The engine makes sharp metallic knocks that change with the throttle
opening.
|
Preliminary Checks
|
| • | Refer to Important Preliminary Checks Before Starting. |
| • | Refer to Visual/Physical Checks |
|
Fuel
System
|
| • | Inspect for conditions that can cause an engine to run lean, indicating
that the long-term fuel trim is significantly in the positive range. Refer
to
DTC P0171 Fuel Trim System Lean
in Diagnostic Aids . |
|
Ignition
System
| Inspect
the spark plugs for proper heat range and reach.
|
Engine Cooling System
| Inspect for the
following obvious overheating problems:
| • | Restricted air flow to the radiator, or restricted water flow
through the radiator |
| • | Incorrect coolant solution--The coolant should be a 50/50
mix of GM 1052753 or equivalent antifreeze coolant and water. |
|
Engine
Mechanical
|
| • | Inspect for excessive oil in the combustion chamber--Check
for leaking valve seals. Refer to Oil Consumption Diagnosis
in Engine Mechanical. |
| • | Inspect the combustion chambers for excessive carbon buildup.
Clean the chambers using Top™ engine cleaner. Follow the instructions
on the can. |
| • | Inspect for incorrect basic engine parts. Check the following
engine components: |
| - | Other engine components, as applicable |
|
Additional
Checks
|
| • | Inspect the Transaxle Range Switch input with the vehicle in drive
and with the gear selector in drive or overdrive. |
| • | Test the TCC operation. The TCC applying too soon can cause the
engine to spark knock. Refer to
Torque Converter Diagnosis
in Automatic Transaxle - 4T65-E. |
| • | If the scan tool readings are normal and if there are no engine
mechanical faults, fill the fuel tank with a known quality gasoline that has
a minimum octane reading of 87, and re-evaluate the vehicle performance. |
|
