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 P0172 or P0175
. |
| • | 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 P0171 or P0174
. |
|
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: |
| • | An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage 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 one of the following procedures: |
| • | 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
|
| • | Ensure that the engine coolant temperature (ECT) is not above 130°C (266°F). This condition causes the powertrain control module (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. |
| • | Inspect the following components for incorrect basic engine parts: |
Refer to the appropriate procedures in Engine Mechanical 8.1L.
|
Additional
Checks
|
| • | Inspect the following components of the exhaust system for possible restrictions: |
| - | The exhaust system for damaged or collapsed pipes |
| - | The exhaust manifold for a collapsed inner wall |
| - | The mufflers for heat distress or possible internal failure |
| - | The TWC for possible plugged conditions--Compare 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. |
|
