Detonation/Spark Knock
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
Symptoms
,
Important Preliminary Checks Before Starting. |
| • | Check the PCM grounds for being clean, tight and in their proper
locations. |
| • | If the scan tool readings are normal (refer to supporting text
of the Powertrain On-Board Diagnostic (OBD) System Check) and there
are no engine mechanical faults. Fill the fuel tank with a premium gasoline
that has a minimum octane reading of 92 and re-evaluate vehicle
performance. |
|
Fuel System
|
| • | Check for a restricted fuel filter. |
| • | Check items which can cause an engine to run rich (long term fuel
trim near -99%). |
| • | Check items that can cause an engine to run lean (long term fuel
trim near 100%). |
|
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
the radiator. |
|
Engine Mechanical
| Check for the following conditions:
| • | Excessive oil in the combustion chamber may indicate leaking valve
seals. Refer to Oil Consumption Diagnosis
. |
| • | Low cylinder compression. Refer to Engine Compression Test
. |
| • | Combustion chambers for excessive carbon buildup. Clean using
Top Engine cleaner. Follow the instructions on the container. |
| • | Incorrect basic engine parts. Inspect the following: |
Refer to Base Engine Misfire Diagnosis
.
|
Additional Checks
|
| • | Check for proper Trans Range switch operation. |
|
