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
|
| • | Search for service bulletins. |
|
Fuel
System
|
| • | Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis
. |
| • | 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 and reach. Refer to
General Information. |
| • | 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. |
| • | Inoperative electric cooling fan circuit(s). |
| • | Correct coolant solution should be a 50/50 mix of Dexcool or equivalent
antifreeze coolant and water. Refer to Engine Cooling. |
|
Engine
Mechanical
|
| • | Excessive oil in combustion chamber-Leaking valve seals.
Refer to the Engine Mechanical
portion
of the service manual. |
| • | Low cylinder compression. Refer to the Engine
Mechanical
portion of the service manual. |
| • | Combustion chambers for excessive carbon buildup. Clean using
Top engine cleaner. Follow instructions on can. |
| • | For incorrect basic engine parts. Inspect the following: |
| • | Refer to 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 TCC operation. TCC applying too soon can cause the engine
to spark knock. Refer to Torque Converter Clutch in Transaxle 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. |
|
