Inspections
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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. - | Water intrusion in the heated oxygen sensor (HO2S) connector |
- | Engine oil contaminated by fuel |
- | 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. |
• | Inspect for an inaccurate speedometer. |
• | Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. Refer to
Scan Tool Data List . |
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Ignition System
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• | 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: |
- | Verify that the spark plugs are of the correct type. |
• | Inspect for proper ignition voltage output with the
J 26792 (SA9199Z) Spark Tester. |
• | 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 . |
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Engine Cooling System
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• | 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. |
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Engine Mechanical
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• | Inspect engine mechanical for the following: |
- | 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: |
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Additional Inspections
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• | Visually and physically inspect the vacuum hoses for splits, kinks, and proper connections and routing as shown on the Vehicle Emission Control Information label. |
• | Inspect the transmission torque converter clutch (TCC) operation. The scan tool should indicate an RPM drop when the system commands the TCC ON. |
• | Inspect the exhaust system for a possible restriction. Inspect for the following: |
- | The exhaust system for damaged or collapsed pipes |
- | The mufflers for heat distress or possible internal failure |
• | 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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