Checks
| Action
|
DEFINITION: Engine power variation during steady throttle
or cruise. The vehicle appears to speed up and slow down, with no
change in the accelerator pedal position.
|
Preliminary
|
| • | Be sure the driver understands the operation of the transmission
torque converter clutch (TCC) and A/C compressor operation as explained in
the owner's manual. Inform the customer how the TCC and the
A/C clutch operate. |
|
Sensor/System
|
| • | Test the heated oxygen sensors (HO2S). The HO2S should quickly
respond to the different throttle positions. If the sensors are unresponsive,
inspect the sensors for silicon or for other contaminates from the fuel
or from the use of an improper room temperature vulcanizing (RTV)
sealant. The sensors may have a white powdery coating which will
cause a high but false signal voltage, indicating a rich exhaust indication.
The powertrain control module (PCM) will then reduce the amount
of fuel that is delivered to the engine, causing a severe driveability
problem. |
|
Fuel System
|
| • | Ensure that each injector harness is connected to the correct
injector and cylinder according to the firing order. The firing order is 1-8-7-2-6-5-4-3.
Relocate the injector harnesses as necessary. |
| • | Test the items which can cause an engine to run rich, where the
long term fuel trim is near -13 percent. For a rich condition,
refer to
DTC P0131 or P0151
and
DTC P0132 or P0152
. |
|
Ignition System
|
| • | Wet down the secondary ignition system with water from a spray
bottle. Wetting down the secondary ignition system may help locate damaged
or deteriorated components. Look and listen for arcing or misfiring
as you apply the water. |
| • | Remove the spark plugs and inspect for the following conditions: |
| • | To properly inspect the spark plugs or to correct a problem, refer
to the following procedures: |
| • | An improper spark plug gap causes a driveability condition. Gap
the spark plugs using a wire gauge gap tool. Refer to
Spark Plug Replacement
. |
| • | Determine the cause of the fouling before replacing the spark
plugs if the spark plugs are gas, coolant or oil fouled. Refer to
DTC P0172 or P0175
for diagnosis of the
rich condition. Refer to
Spark Plug Inspection
for diagnosis of coolant or oil fouled spark plugs. |
|
Engine Mechanical
| Ensure that the engine coolant temperature is not above
130°C (266°F). This condition causes the PCM to operate in Engine
Coolant Over Temperature-Fuel Disabled Mode. While in Engine
Coolant Over Temperature-Fuel Disabled Mode, the PCM turns
fuel OFF to 4 cylinders at a time in order to keep engine temperatures
from reaching damaging levels. The system perceives Engine Coolant
Over Temperature-Fuel Disabled Mode as a lack of power, a miss,
or a rough idle. If the vehicle operates in Engine Coolant Over
Temperature-Fuel Disabled Mode, refer to
Engine Overheating
in Engine Cooling for diagnosis.
|
Additional Checks
|
| • | Inspect vacuum hoses for splits, for kinks, and for proper connections
and routing as shown on Vehicle Emission Control Information label.
Refer to
Emission Hose Routing Diagram
. |
| • | Test the transmission torque converter clutch (TCC) operation.
A TCC applying too soon can cause the engine to spark knock. Refer to
Torque Converter Diagnosis
in Automatic
Transmission - 4L60 E. |
|
