Checks
| 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
|
| • | Refer to Important Preliminary Checks. |
| • | Refer to Visual/Physical Checks |
| • | Ask about the owner's driving habits. |
| - | Is the A/C on full time (Defroster mode on)? |
| - | Are the tires at the correct pressure? |
| - | Are excessively heavy loads being carried? |
| - | Is acceleration too much, too often? |
|
Fuel
System
|
| • | Inspect for fuel in the pressure regulator vacuum hose. |
|
Sensor/System
|
| • | Test for the proper calibration of the speedometer. Connect the J 33431-C
signal generator to
the vehicle speed sensor (VSS) electrical connector. Turn the ignition and
the tester on and monitor the speedometer. |
|
Ignition
System
|
| • | Test for proper ignition voltage output using the following procedure: |
| - | Clip the J 26792
spark tester to engine ground. |
| - | Connect one end of a spark plug wire to the spark tester. Leave
the other end of the spark plug wire connected 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. Spark should
be observed. |
| - | Repeat the above steps for each coil. |
| • | If adequate spark is not present at the coils, inspect or test
for the following conditions: |
| - | Inspect the coils for cracks, carbon tracking/arcing, or a resistance
value outside the 5000 - 8000 ohms range. |
| - | Inspect the spark plug wires for signs of arcing/cross firing,
cracks, carbon tracking, plug boot damage, pinched wires, improper routing,
or a resistance value other than 600 ohms per ft. (1968 ohms
per meter). |
| | Important: Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent problem. Ignition components arc to ground when
a secondary component is faulty.
|
| - | Test for a defective module. |
| - | Inspect the ignition system wiring for a 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. |
| • | Test for the following intermittent ignition system conditions: |
| - | An intermittent CKP sensor 24X signal. |
| - | An intermittent ignition feed circuit or sensor ground circuit
to the CKP sensor or the camshaft position (CMP) sensor. |
| - | An intermittent 3X reference signal. |
| - | An intermittent CMP signal |
|
Engine
Cooling System
|
| • | Inspect the engine coolant level for being low. |
| • | Test for an incorrect or faulty engine thermostat. Refer to
Thermostat Diagnosis
in Engine Cooling. |
|
Engine
Mechanical
|
| • | Inspect or test the following engine mechanical components: |
| - | Test for sticking or leaking valves. |
| - | Inspect for worn camshaft lobe(s). |
| - | Inspect for bent push rods. |
| - | Inspect for worn rocker arms. |
| - | Inspect for broken valve springs. |
| - | Test for excessive oil in the combustion chambers or leaking valve
seals. |
| • | Inspect for incorrect basic engine parts. Inspect the following: |
|
Additional
Checks
|
| • | Test the TCC operation. |
| • | Inspect the exhaust system for restriction: |
| - | Inspect the exhaust system for damaged or collapsed pipes. |
| - | Inspect the mufflers for heat distress or possible internal failure. |
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