Lack of Power, Sluggish or Spongy
Checks
| Action
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DEFINITION: The engine
delivers less than expected power. Little or no increase in speed when the
accelerator pedal is pushed down part way.
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Preliminary Inspections
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• | Refer to Important Preliminary Inspections Before Starting in
Symptoms
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Fuel System
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• | 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. |
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Sensor/System
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• | 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 Extended Travel Brake Switch Circuit
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Ignition System
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• | 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/listen for arcing or misfiring as water is applied. |
• | Test for proper ignition voltage output with spark tester J 26792
. |
• | 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 procedure in Engine Electrical: |
• | 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
in Engine Electrical. |
• | 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: |
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Engine Mechanical
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• | 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 OverTemperature-Fuel
Disabled Mode, the PCM will turn the fuel off to 4 cylinders
at a time to keep engine temperatures from reaching damaging levels.
The system perceives the Engine Coolant OverTemperature-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 incorrect basic engine parts, inspect the following: |
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Additional Inspections
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• | 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 Three-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. |
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