Check
| Action
|
Definition: A mild
to severe ping, usually worse under acceleration. The engine makes sharp metallic
knocks that change with the throttle opening.
|
Preliminary
Checks
| Refer to
Symptoms
.
Verify the customer concern.
|
Cooling System Checks
|
| • | Inspect for a low engine coolant level. |
| • | Inspect for the proper tension on the drive belts. |
| • | Inspect for restricted air flow through the radiator, or restricted
coolant flow. |
| • | Inspect for a correct coolant mixture. |
|
Sensor Check
| Inspect for an engine coolant temperature (ECT) sensor
that has a shift in value. Refer to
Temperature Versus Resistance
.
|
Fuel System Checks
|
| • | Check if a lean system causes this 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
150. |
| • | Check for a poor fuel quality and a proper octane rating. |
| • | If the fuel trim readings are normal and there are no engine mechanical
concerns, then fill the fuel tank with a known good fuel and reevaluate the
vehicles performance. |
|
Ignition System Checks
|
| • | Inspect the spark plugs for their proper heat range and gap. |
| • | Inspect the knock sensor (KS) system operation. |
| • | Inspect the ignition timing. |
|
Engine Mechanical Checks
|
| • | Inspect for carbon build up. Remove the carbon with a top engine
cleaner. Follow the instructions on the can. |
| • | Inspect the combustion chamber pressure by performing a compression
test. |
|
Additional Checks
|
| • | Inspect the torque converter clutch (TCC) operation. Refer to
Symptom Diagnosis
in Automatic Transmission. |
| • | Check the service bulletins for calibration updates. |
|
