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
|
| • | Road test the vehicle and determine the severity of the complaint. |
|
Cooling System Checks
|
| • | Check for any obvious overheating problems. Refer to
Engine Overheating
in Engine Cooling. |
| • | Check for a low engine coolant level. Refer to
Loss of Coolant
in Engine Cooling. |
| • | Check for a loose water pump belt. |
| • | Check for restricted air flow through the radiator, or restricted
coolant flow. |
| • | Check for a correct coolant solution. The solution should be a
50/50 mix of anti-freeze and 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
|
| • | Check to determine if a lean system causes the condition. Drive
the vehicle at the speed of the complaint. Monitoring the Fuel Trim will help
identify the problem. If the system is Lean, the Long Term Fuel Trim will
be more than 20 percent. |
| • | Check for poor fuel quality and proper octane rating. If the scan
tool readings are normal and there are no engine mechanical faults, fill the
fuel tank with a premium gasoline that has a minimum octane rating of
92 and re-evaluate vehicle performance. |
|
Ignition System
Checks
| Check
the spark plugs for the proper heat range and gap. Refer to
Ignition System Specifications
.
|
Engine Mechanical Checks
|
| • | Check for carbon buildup. Remove the carbon with a top engine
cleaner. Follow the instructions on the can. |
| • | Check for incorrect basic engine parts such as cam, heads, pistons,
etc. |
|
Additional Checks
|
| • | Check for the proper operation of the air induction system. |
| • | Check the Service Bulletins for any updates. |
|
