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. |
• | 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 GM 1052753 or
equivalent antifreeze coolant and water. Refer to
Coolant Description
in Engine Cooling. |
|
Engine Mechanical
|
• | Excessive oil in combustion chamber-Leaking valve seals.
Refer toOil Consumption Diagnosis
in 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: |
|
Additional Checks
|
• | Check the Transaxle Range Switch input with the vehicle in drive
and the gear selector in drive or overdrive. |
• | 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. |
|