Test/Inspection
| Action
|
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.
|
Preliminary
|
| • | Inquire about the owner's driving habits: |
| - | Is the A/C ON full time (Defroster mode ON)? |
| - | Are the tires inflated to the correct pressure? |
| - | Are excessively heavy loads being carried? |
| - | Is acceleration too much, too often? |
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Fuel System
|
| • | Inspect for fuel in the pressure regulator vacuum hose. |
|
Sensor/System
|
| • | Monitor the 24X Crankshaft Position and Camshaft Position Sensors
on scan tool. If both are not responding, test the sensor feed circuit. Both
sensors use a separate feed circuit but are internally connected to power.
Test all 24X and CMP sensor circuits for intermittents. Refer to
Testing for Intermittent Conditions and Poor Connections
in
Wiring Systems. |
| • | Monitor the 3X parameter on the scan tool. If the 3X is not responding,
inspect the 7X CKP Sensor and circuits for intermittents. Inspect the IC circuit,
Bypass circuit, 3X Reference High Circuit, and the 3X Reference Low circuit
for intermittents. If these circuits become open, or shorted may not set a
DTC immediately, but are capable of causing driveability complaints. Refer
to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. |
| • | Verify proper calibration of the speedometer. |
|
Ignition System
|
| • | Inspect for proper ignition voltage output using the following
steps: |
| 1. | Attach the J 26792
spark tester to engine ground. |
| 2. | Connect the spark plug end of the spark plug wire to the J 26792
spark tester; leave the
other end of the spark plug wire connected to the coil being tested. |
| 3. | Connect the spark plug end of the companion spark plug wire to
ground. |
The companion spark plug wire is the wire attached to the corresponding
coil tower.
| 4. | Crank the engine while observing the J 26792
spark tester; a spark should be observed. |
| 5. | Repeat the above steps for each coil. |
| • | If spark is not present at the coils, inspect for the following
conditions: |
| - | Coils--Cracks, carbon tracking/arcing, or a resistance value
outside the specified range. |
Coil Resistance
5000-8000ohms (5K-8Kohms) | - | 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
600ohms per foot (1 968ohms per meter).
| | Important: : Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent problem. Ignition voltage will arc to ground when
a secondary component is faulty.
|
| - | Defective ignition module. |
| - | Ignition system wiring--Loose ignition module feed or ground
connection, or damaged system wiring. |
| • | Remove spark plugs and inspect for the following conditions: |
| - | 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. |
|
Engine Cooling
|
| • | Inspect the engine coolant level for being low. |
| • | Inspect for an incorrect or faulty engine thermostat. Refer to
Thermostat Diagnosis
in Engine Cooling. |
|
Engine Mechanical
|
| • | Inspect for the following engine mechanical concerns:
|
| - | Sticking or leaking valves |
| - | Excessive oil in the combustion chamber or leaking valve seals |
| • | Inspect for incorrect basic engine parts including the following:
|
| • | Refer to Engine Mechanical for diagnostic procedures.
|
|
Additional
|
| • | Test the torque converter clutch (TCC) operation. |
| • | Inspect the exhaust system for possible restrictions. Inspect
for the following: |
| - | Inspect the exhaust system for damaged or collapsed pipes. |
| - | Inspect the mufflers for heat distress or possible internal failure. |
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