Lack of Power, Sluggish or Spongy
Checks
| Action
|
DEFINITION: Engine
delivers less than expected power. Little or no increase in speed when
the accelerator pedal is pushed down part way.
|
Preliminary Checks
|
| • | 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 four ignition coils and four 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 that cause an engine to run rich long term fuel
trim near -13 percent. For a rich condition, refer to
DTC P0132 or P0152
. |
| • | Inspect the items that can cause an engine to run lean long term
fuel trim near 24 percent For a lean condition, refer to
DTC P0131 or P0151
. |
|
Sensor/System
| Use a scan
tool in order to monitor the knock sensor (KS) system for excessive spark
retard activity. Refer to
Knock Sensor (KS) System Description
.
|
Ignition System
|
| • | Inspect both injector fuses for being open. An open injector fuse
causes four ignition coils and four 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. |
| • | Inspect for proper ignition voltage output with J 26792
Spark Tester . |
| • | Remove the spark plugs and check for the following: |
Refer to
Spark Plug Inspection
.
| • | An improper spark plug gap will cause a driveability problem.
Gap the spark plugs using a wire gauge gap too. 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. |
| • | Monitor the Misfire Current Counters while driving the vehicle
in the conditions that the misfire occurred. If a cylinder can be located
with a misfire, use the DTC P0300 table for diagnosis. |
|
Engine
Mechanical
|
| • | Verify that the engine coolant temperature (ECT) 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 disable the fuel injectors to four cylinders
at a time 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 for diagnosis. |
| • | Excessive oil in combustion chamber--Leaking valve seals.
Refer to
Oil Consumption Diagnosis
in Engine Mechanical 4.8L, 5.3L, 6.0L. |
| • | For incorrect basic engine parts. Inspect the following: |
Refer to Engine/Engine Mechanical.
|
Additional Checks
|
| • | Inspect the exhaust system for possible restrictions. Inspect
for the following: |
| - | Inspect the exhaust system for damaged or collapsed pipes. |
| - | Inspect the exhaust manifold for a collapsed inner wall. |
| - | Inspect the mufflers for heat distress or possible internal failure. |
| - | Inspect for possible plugged three-way catalytic converters by
comparing the exhaust system back pressure on each side of engine. Check
back pressure by removing secondary air injection
(AIR) check valves near exhaust manifolds. Refer to
Restricted Exhaust
in Engine Exhaust. |
|
