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 in
Symptoms
. |
| • | Refer to Visual/Physical Checks in
Symptoms
. |
| • | 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? |
|
Fuel System
|
| • | Check the fuel injectors using the following procedures: |
| • | Ensure each injector harness is connected to the correct injector/cylinder. |
| • | Check for fuel in the pressure regulator vacuum hose. |
|
Sensor/System
|
| • | Check for proper calibration of speedometer. Connect J 33431-C
signal generator to VSS electrical
connector. Ignition ON, tester ON and monitor the speedometer. |
|
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 J 26792
spark tester; a spark should be observed. |
| - | Repeat the above steps for each coil. |
| • | If spark is not present at the plug, check for the following conditions: |
| - | Coil(s) - Cracks, carbon tracking/arcing, or a secondary 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
600 ohms per/ft.
| | 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 components: |
| | Important:: If carbon tracking is detected on any component replace that component
and it's mate. Carbon tracking on the porcelain and pitting on the plug wire
contact.
|
| - | Burned or damaged electrodes |
| - | Improper heat range or reach - refer to
Spark Plug Usage
in Engine Electrical. |
| • | If spark plugs are gas or oil fouled, the cause of the fouling
must be determined before replacing the spark plugs. Refer to
Oil Consumption Diagnosis
in Engine Mechanical. |
|
Engine Cooling System
|
| • | Check engine coolant level for being low. Refer to
Loss of Coolant
in Engine Cooling. |
|
Engine Mechanical
|
| • | Check engine mechanical for the following conditions: |
| - | Sticking or leaking valves |
| - | Excessive oil in combustion chamber-Leaking valve seals |
| • | For incorrect basic engine parts inspect for the following components: |
Refer to
Engine Compression Test
and
Cylinder Leakage Test
in Engine
Mechanical.
|
Additional Checks
|
| • | Check exhaust system for possible restriction: |
| - | Inspect exhaust system for damaged or collapsed pipes. |
| - | Inspect mufflers for heat distress or possible internal failure. |
|
