Checks
| Action
|
DEFINITION: Fuel economy, as measured by an actual road test is noticeably lower
than expected. Also, economy is noticeably lower than the fuel economy was on this
vehicle at one time, as previously shown by an actual road test.
|
Preliminary
|
| • | Refer to Important Preliminary Checks. |
| • | Refer to Visual/Physical Checks. |
| • | Review the owner's driving habits. |
| - | Is A/C ON full time (Defroster mode ON)? |
| - | Are tires at correct pressure? |
| - | Are tires and wheels the correct size? |
| - | Are excessively heavy loads being carried? |
| - | Is acceleration too much, too often? |
|
Fuel System
|
| • | Inspect the fuel injectors using the following tests: |
| • | Ensure each injector harness is connected to the correct injector/cylinder. |
| • | Inspect for fuel in the pressure regulator vacuum hose. |
|
Sensor/System
|
| • | Inspect the air intake system and crankcase for air leaks. |
| • | Test for proper calibration of speedometer. Connect the J 33431-C
Signal Generator and Instrument Panel Tester
to the vehicle speed sensor (VSS) electrical connector. Turn ON the ignition, with
the engine OFF. With the tester ON, monitor the speedometer. |
|
Ignition System
|
| • | Test for proper ignition voltage output using the following steps: |
| 1. | Clip the J 26792
spark tester to engine ground. |
| 2. | Connect one end of a spark plug wire to the J 26792
. Connect the other end of the spark plug wire to the coil being
tested. |
| 3. | Connect another spark plug wire between the remaining tower of the coil
being tested and ground. |
| 4. | Crank the engine while observing the J 26792
. A spark should be observed. |
| 5. | Repeat the above steps for each coil. |
| • | If spark is not present at the coils, test for the following conditions: |
| - | Coils--Cracks, carbon tracking/arcing, or a secondary resistance
value outside the specified range |
Coil Resistance
5,000-8,000 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
9840 ohms per meter (3000 ohms
per foot)
Spark Plug Wire Resistance Police
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 condition. 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 inspect 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. Refer to
Spark Plug Inspection
. |
|
Engine Cooling System
|
| • | Inspect the engine coolant level for being low. Refer to
Loss of Coolant
in Engine Cooling. |
| • | Inspect and test for an incorrect or faulty engine thermostat. Refer to
Thermostat Diagnosis
in Engine Cooling. |
|
Engine Mechanical
|
| • | Inspect engine mechanical for the following: |
| - | Sticking or leaking valves |
| - | Excess oil in combustion chamber--Inspect for leaking valve seals. |
| • | Inspect for incorrect engine parts, such as the following basic components: |
Refer to
Symptoms - Engine Mechanical
in
Engine Mechanical-3.8L.
|
Additional Checks
|
| • | Test the exhaust system for a possible restriction. Inspect for the following: |
| - | Inspect the exhaust system for damaged or collapsed pipes. |
| - | Inspect the mufflers for heat distress or possible internal failure. |
| - | For possible plugged 3-way catalytic converter--Refer to
Restricted Exhaust
in Engine Exhaust. |
|
