Detonation/Spark Knock
Checks
| Action
|
DEFINITION: The engine makes
a mild to severe pinging noise, which is usually worse during acceleration.
The engine makes sharp metallic knocks that change with the
throttle opening.
|
Preliminary Checks
|
| • | Search the service bulletins. |
|
Fuel System
|
| • | Check for conditions that can cause an engine to run lean, where
the long-term fuel trim is significantly in the positive range. Refer to Diagnostic
Aids for
DTC P0171
. |
|
Ignition System
|
| • | Check the knock sensor (KS) system for no retard timing. |
|
Engine Cooling System
| Check for obvious overheating problems, including the following conditions:
| • | Restricted air flow to the radiator |
| • | Restricted water flow through the radiator |
| • | Inoperative electric cooling fan circuits |
| • | Incorrect thermostat operation |
The correct coolant solution should be a 50/50 mix of Dexcool® or
an equivalent mixture of antifreeze coolant and water. Refer to
Engine Overheating
in Engine Cooling.
|
Engine Mechanical
|
| • | Excessive oil in the combustion chamber. This condition can be
caused by leaking valve seals. Refer to
Oil Consumption Diagnosis
in Engine Mechanical 2.4L. |
| • | Excessive carbon buildup--Check the combustion chambers.
Clean the chambers with Top engine cleaner. Follow the instructions on the
can. |
| • | Incorrect basic engine parts. Inspect the following: |
| - | Other components, as applicable. |
|
Additional Checks
|
| • | Check for proper operation of the manifold absolute pressure (MAP)
sensor. Ensure that the MAP sensor is not out of range. |
| • | Check the park/neutral position (PNP) switch input with the vehicle
in drive, and with the gear selector in drive or in overdrive. |
| • | Check the torque converter clutch (TCC) operation. Applying the
TCC too soon can cause the engine to spark knock. Refer to
Road Test
for 4T40 or
Road Test
for 3T40 in Automatic Transmission. |
| • | If the scan tool readings are normal, and if there are no engine
mechanical malfunctions, fill the fuel tank with a known quality gasoline
that has a minimum octane reading of 87. Re-evaluate the vehicle
performance. |
|
