Inspections
| Action
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DEFINITION: Fuel economy, as measured by an actual road test, is noticeably
lower than expected. Also, fuel economy is noticeably lower than the economy was
on this vehicle at one time, as previously shown by an actual road test.
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Preliminary
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• | Discuss driving habits with the owner. |
- | Is the A/C ON or the Defroster mode ON full time? |
- | Are the tires at the correct pressure? |
- | Are the wheels and tires the correct size? |
- | Are there excessively heavy loads being carried? |
- | Is the acceleration rate too much, too often? |
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Fuel System
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• | Discuss with the owner the type, quality, and alcohol content of the fuel.
Oxygenated fuels have lower energy and may deliver reduced fuel economy. Refer to
Alcohol/Contaminants-in-Fuel Diagnosis
. |
• | Inspect that each fuel injector harness is connected to the correct injector
and cylinder. Relocate the injector harnesses, as necessary. |
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Sensor/System
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• | Inspect for the following that may cause the engine to run rich: |
Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section. - | Any water intrusion in the heated oxygen sensor (HO2S) connector |
- | The engine oil contaminated by fuel |
- | Any vacuum hoses that are split, kinked, or improperly connected |
- | An air intake duct that is collapsed or restricted |
• | Inspect the air intake system and crankcase for air leaks. |
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Ignition System
|
• | In order to properly inspect the spark plugs or to correct a condition,
refer to the following procedures: |
• | Remove spark plugs and inspect for the following conditions: |
- | Verify that the spark plugs are of the correct type. |
• | An improper spark plug gap will cause a driveability condition. Gap the
spark plugs using a wire gage gap tool. |
• | Determine the cause of the fouling before replacing the spark plugs. |
• | Inspect for damaged or misaligned spark plug boots. |
• | Inspect the electronic ignition (EI) module for proper ground connection. |
• | Monitor the Misfire Current Counters while driving the vehicle in the
conditions that the symptom occurred. If a misfiring cylinder can be located, use
the DTC P0300 table for diagnosis. Refer to
DTC P0300
. |
|
Engine Cooling System
|
• | Inspect the engine coolant level for being low. Refer to
Loss of Coolant
in Engine Cooling. |
• | Inspect the engine thermostat for proper operation and for the correct
heat range. Refer to
Thermostat Diagnosis
in
Engine Cooling. |
|
Engine Mechanical
|
• | Inspect engine mechanical for the following conditions: |
- | Sticking or leaking valves |
- | Excessive oil in combustion chamber or leaking valve seals. |
- | For more information, refer to one or more of the following procedures
in Engine Mechanical: |
• | For incorrect basic engine parts, inspect the following components: |
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Additional Inspections
|
• | Visually and physically check the vacuum hoses for splits, kinks, and
proper connections and routing as shown on Vehicle Emission Control Information label. |
• | Inspect the transmission torque converter clutch (TCC) operation. The
scan tool should indicate a RPM drop, when the system commands the TCC ON. |
• | Inspect the exhaust system for a possible restriction. Inspect for the
following conditions: |
- | The exhaust system for damaged or collapsed pipes |
- | The mufflers for heat distress or possible internal failure |
- | The catalytic converters for being plugged--Refer to
Restricted Exhaust
in Engine Exhaust. |
• | Inspect the brake system for dragging or improper operation. Refer to
Symptoms - Hydraulic Brakes
in Hydraulic Brakes.
Verify that the vehicle operator does not drive with a foot on the brake pedal. |
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