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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| • | Observe the owners driving habits: |
| - | Is the 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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| • | Ensure each injector harness is connected to the correct injector/cylinder. |
| • | Inspect for fuel in the pressure regulator vacuum hose. |
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Sensor/System
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| • | Inspect for 24X crankshaft position (CKP) and camshaft position
(CMP) sensors on the scan tool. If both are not responding, inspect the sensor
feed circuit. |
| • | Inspect the air intake system and crankcase for air leaks. |
| • | Inspect for proper calibration of the speedometer. Connect the J 33431-B
signal generator to
the VSS electrical connector. Ignition on, tester on, and monitor the speedometer. |
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Ignition System
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| • | Inspect for proper ignition voltage output using the following
steps: |
| - | Clip the J 26792
spark tester to engine ground. |
| - | Connect one end of a spark plug wire to the J 26792
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 J 26792
spark tester. A spark should be observed. |
| - | Repeat the above steps for each coil. |
| • | If spark is not present at the plugs, inspect for the following
conditions: |
| - | Inspect the coils for cracks, carbon tracking/arcing or a resistance
value outside the specified range. |
Coil Resistance
5K-7K ohms (5,000-7,000 ohms). | - | Inspect the spark plug wires for 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
1 968 ohms per meter (600 ohms per foot).
| | 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 the spark plugs and inspect for the following: |
| - | Burned or damaged electrodes |
| - | Improper heat range or reach |
| • | If the 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
|
| • | Inspect the engine coolant for proper level. |
| • | Inspect for an incorrect or faulty engine thermostat. Refer to
Thermostat Diagnosis
in 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: |
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Additional Checks
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| • | Inspect the exhaust system for possible restriction: |
| - | Inspect the exhaust system for damaged or collapsed pipes. |
| - | Inspect the mufflers for heat distress or possible internal failure. |
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