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 Dex -Cool®
or equivalent antifreeze coolant and clean, drinkable, water. Refer to Engine
Cooling. |
|
Engine Mechanical
|
| • | Excessive oil in combustion chamber, leaking valve seals. Refer
to in Engine Mechanical. |
| • | Low cylinder compression. Refer to in the Engine Mechanical. |
| • | 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 in Engine Mechanical. |
|
Additional Checks
|
| • | Check the Transmission Range 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 Transmission 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. |
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