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
. |
• | Inspect the intake air ducts for the following conditions: |
- | Improperly installed hoses |
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Fuel System
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Sensor/System
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• | Use a scan tool in order to monitor the knock sensor (KS) system
for excessive spark retard activity. Refer to
Detonation/Spark Knock
. |
• | Check for proper operation of the throttle control system components.
Use the scan tool special functions to actuate the system. Verify that the
throttle opens to 100 percent. With a scan tool. monitor the following
throttle control system components: |
- | Throttle position sensors |
- | Accelerator pedal position sensors |
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Ignition System
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• | Test for secondary ignition leakage. Refer to the procedure in
the Diagnostic Aids portion of
Ignition System Check
. |
• | Remove the spark plugs and inspect for the following conditions: |
• | 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
Spark Plug Visual Diagnosis
in Engine Electrical: |
- | For diagnosis of coolant contaminated spark plugs, refer to
Loss of Coolant
in Engine Cooling. |
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Engine Mechanical
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• | For incorrect basic engine parts, inspect the following: |
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Additional Inspections
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• | Inspect the exhaust system for possible restrictions: |
- | The exhaust system for physical damage |
- | The mufflers for heat distress or possible internal failure |
- | The catalytic converters for possible plugged pipes by comparing
the exhaust system back pressure on each side of engine. Refer to
Restricted Exhaust System Check
. |
• | Test for proper operation of the intake resonance switchover valve
and the intake plenum switchover valve. Refer to
Multi Ram System Diagnosis
. |
• | Test the transmission torque converter clutch (TCC) for proper
operation. Refer to
Torque Converter Diagnosis
in Automatic Transmission-4L30-E. |
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