Checks
| Action
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DEFINITION: The fuel economy, as measured by an actual road test, is noticeably lower than expected. The fuel economy is also noticeably lower than previously shown by an actual road test.
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Preliminary
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| • | Refer to Important Preliminary Checks. |
| • | Refer to Visual/Physical Checks |
| • | Check owners driving habits. |
| - | Is A/C ON full time and is the Defroster mode ON? |
| - | Are the tires at the correct pressure? |
| - | Is the vehicle carrying excessively heavy loads? |
| - | Is the acceleration too much, too often? |
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Fuel System
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| • | Check the fuel injectors using the following tests: |
| • | Ensure that each injector harness is connected to the correct injector and cylinder. |
| • | Inspect for fuel in the pressure regulator vacuum hose. |
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Sensor/System
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| • | Test for proper speedometer calibration. Connect a
J 33431-C
Signal Generator to the VSS electrical connector. Turn ON the ignition, with the engine OFF, and with the tester ON, monitor the
speedometer. |
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Ignition System
| Test for proper ignition voltage output using the following steps:
- Clip the spark tester
J 26792
to engine ground.
- Connect one end of a spark plug wire to the spark tester; leave the other end of the spark plug wire to the coil being tested.
- Connect one end of another spark plug wire to the other coil tower; connect the other end of the spark plug wire to ground.
- Crank the engine while observing the spark tester; a spark should be observed.
- Repeat the above steps for each coil.
- If no spark is present at the coils, test for the following conditions:
| - | The coils--Inspect for cracks, for carbon tracking or arcing, or for a secondary resistance value that is outside the specified range. |
Coil Resistance
5,000-8,000 ohms (5K-8K ohms) | - | The spark plug wires--Inspect for signs of arcing or cross-firing, for cracks, for carbon tracking, for plug boot damage, for pinches, for improper routing, or for a resistance value that is outside the specified range. |
Spark Plug Wire Resistance
600 ohms per ft.
| | Important: Spraying the secondary ignition wires with a light mist of water may help to locate an intermittent problem. The ignition components will arc to ground when a secondary component is faulty.
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| - | The ignition system wiring--Inspect for a loose ignition module feed or ground connection, or for damaged system wiring. |
- Remove spark plugs and inspect for the following conditions:
| - | Burned or damaged electrodes |
| - | Improper heat range or reach |
- If the spark plugs are gas or oil fouled, determine the cause of the fouling before you replace the spark plugs.
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Engine Cooling System
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| • | Inspect the engine coolant level for being low. |
| • | Inspect and test for an incorrect or a faulty engine thermostat. Refer to
Thermostat Diagnosis
in Engine Cooling. |
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Engine Mechanical
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| • | Inspect engine mechanical components for the following conditions: |
| - | Sticking or leaking valves |
| - | Excessive oil in the combustion chamber that is caused by leaking valve seals |
| • | Inspect for incorrect basic engine parts. Inspect the following components: |
| - | Other components, as appropriate |
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Additional Checks
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| • | Test the exhaust system for possible restrictions. Inspect for the following conditions: |
| - | Damaged or collapsed pipes |
| - | Heat distress or possible internal failure in the muffler |
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