Lack of Power, Sluggish or Spongy
Checks
| Action
|
DEFINITION: The engine
delivers less than expected power. Little or no increase in speed when the
accelerator pedal is pushed down part way.
|
Preliminary
Inspections
|
| • | Inspect the powertrain control module (PCM) grounds for being
clean, tight, and in the proper locations. Refer to
Engine Controls Schematics
. |
|
Fuel System
|
| • | Inspect both injector fuses for being open. An open injector fuse
causes 4 ignition coils and 4 injectors not to operate. Replace the
fuse. Inspect the ignition coil circuits and the injector circuits
for an intermittent short to ground. |
| • | Inspect the items which can cause an engine to run rich, having
the long term fuel trim near -13 percent. For a rich condition,
refer to
DTC P0131 or P0151
and
DTC P0132 or P0152
. |
| • | Inspect the items that can cause an engine to run lean, having
the long term fuel trim near 23 percent. For a lean condition, refer
to
DTC P0131 or P0151
and
DTC P0132 or P0152
. |
|
Sensor/System
|
| • | An extended travel brake switch that is mis-adjusted, or an extended
travel brake circuit that is open, causes a perceived misfire under heavy
load conditions from a stop. Use a scan tool in order to monitor the
extended travel brake switch parameter. If the scan tool displays
extended travel brake switch applied when the brake pedal is released,
refer to
DTC P1575
. |
|
Ignition System
|
| • | Inspect both injector fuses for being open. An open injector fuse
causes 4 ignition coils and 4 injectors not to operate. Replace the
fuse. Inspect the ignition coil circuit and the injector circuits
for an intermittent short to ground. |
| • | Wet down the secondary ignition system with water from a spray
bottle. Wetting the secondary ignition system may help locate damaged or deteriorated
components. Look and listen for arcing or misfiring as water
is applied. |
| • | Test for proper ignition voltage output with J 26792
Spark Tester. |
| • | Remove the spark plugs and inspect for the following conditions: |
| • | In order to properly inspect the spark plugs or to correct a condition,
refer to the following procedures: |
| • | An improper spark plug gap will cause a driveability concern.
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 the following
procedures in Engine Electrical: |
|
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 will turn the fuel OFF to 4 cylinders
at a time in order to keep engine temperatures from reaching
damaging levels. The system perceives the Engine Coolant Over
Temperature-Fuel Disabled Mode as a lack of power, miss,
or rough idle. If the vehicle operates in Engine Coolant Over Temperature-Fuel
Disabled Mode, refer to
Engine Overheating
in Engine Cooling. |
| • | Excess oil in combustion chamber-Inspect for leaking valve
seals. Refer to
Oil Consumption Diagnosis
in Engine Mechanical--5.7L. |
| • | Inspect for incorrect engine parts, such as the following basic
components: |
|
Additional Inspections
|
| • | Inspect the following exhaust system components for possible restrictions: |
| - | The exhaust system for physical damage |
| - | The exhaust manifold for a collapsed inner wall |
| - | The mufflers for heat distress or possible internal failure |
| - | The 3-way catalytic converters for possible plugged pipes, by
comparing the exhaust system back pressure on each side of engine |
| • | For more information, refer to the following procedures in Engine
Exhaust: |
| • | Test the transmission torque converter clutch (TCC) for proper
operation. Refer to
Torque Converter Diagnosis
in Automatic Transmission-4L60E. |
|
