Checks
| Action
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Definition:
Fuel economy, as measured by an actual road test is noticeably lower than
expected. Also, economy is noticeably lower than it was on this vehicle at
one time, as previously shown by an actual road test.
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Preliminary
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| • | Refer to the Powertrain OBD System Check. |
| • | Refer to Important Preliminary Checks. |
| • | Refer to Visual/Physical Checks |
| • | Check owners driving habits. |
| - | Is A/C ON full time (Defroster mode ON)? |
| - | Are tires at correct pressure? |
| - | Are excessively heavy loads being carried? |
| - | Is acceleration too much, too often? |
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Fuel System
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| • | Check the fuel pressure. Refer to Fuel System Pressure Test. |
| • | Check the fuel injectors. Refer to Fuel Injector Coil/Fuel Injector
Balance test. |
| • | Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel
Testing. |
| • | Ensure each injector harness is connected to the correct injector/cylinder.
Refer to Engine Controls Wiring Diagram. |
| • | Check for fuel in the pressure regulator vacuum hose. |
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Sensor/System
|
| • | Check Air intake system and crankcase for air leaks. Refer to
Air Induction System and Crankcase Ventilation System. |
| • | Check for proper calibration of speedometer. Connect J 33431-B
(Signal Generator) to VSS electrical connector. Ignition ON, tester ON and
monitor the speedometer. |
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Ignition System
|
| • | Check 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 crisp blue
spark should be observed. |
| - | Repeat the above steps for each coil. |
| • | If adequate spark is not present at the coil(s), check for the
following conditions: |
| - | Coil(s) - Cracks, carbon tracking/arcing, or a resistance value
outside the specified range. |
Coil Resistance
5000 - 8000 ohms (5K - 8K ohms) | - | Spark Plug wires - Signs of arcing/cross firing, cracks, carbon
tracking, plug boot damage, pinched, improper routing, or a resistance value
outside the specified range. |
Spark Plug Wire Resistance
7000 ohms (7K ohms)
| | Important: Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent problem. Ignition components will arc to ground
when a secondary component is faulty.
|
| - | Ignition System Wiring - Loose ignition module feed or ground
connection, or damaged system wiring. |
| • | Remove spark plugs and check for the following: |
| - | Burned or damaged electrodes |
| - | Improper heat range or reach |
| • | If spark plugs are gas or oil fouled, the cause of the fouling
must be determined before replacing the spark plugs. |
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Engine Cooling System
|
| • | Check engine coolant level for being low. Refer to Engine Cooling.
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| • | Check for incorrect or faulty engine thermostat. Refer to Engine Cooling.
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Engine Mechanical
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| • | Check engine mechanical for the following: |
| - | Sticking or leaking valves. |
| - | Excessive oil in combustion chamber-Leaking valve seals. |
| • | For incorrect basic engine parts. Inspect for the following: |
| • | Refer to Engine Mechanical
for diagnosis
procedures. |
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Additional Checks
|
| • | Check TCC operation. Refer to Torque Converter Clutch in Transaxle
Diagnosis. |
| • | Check exhaust system for possible restriction. Check for the following: |
| - | Inspect exhaust system for damaged or collapsed pipes. |
| - | Inspect mufflers for heat distress or possible internal failure. |
| - | For possible plugged Three-Way catalytic converter. Refer
to Restricted Exhaust System Check and/or Exhaust System. |
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