Inspection/Test
| Action
|
DEFINITION: Fuel
economy, as measured by an actual road test is noticeably lower than expected.
Also, economy is noticeably lower than at one time, as previously
shown by an actual road test.
|
Preliminary
|
| • | Observe the owners 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 the acceleration too much, too often? |
|
Fuel
System
|
| • | Test the fuel injectors. Refer to the following procedures: |
| • | Ensure each injector harness is connected to the correct injector
and cylinder. |
| • | Inspect for fuel in the pressure regulator vacuum hose. |
|
Sensor/System
|
| • | 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 the crankcase for air leaks. |
| • | Test for proper calibration of the speedometer. Connect the J 33431-B
signal generator to
the VSS electrical connector. Turn the ignition and the tester on and monitor
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 System
|
| • | Inspect for the proper engine coolant level. |
| • | Inspect for an incorrect or faulty engine thermostat. Refer to
Thermostat Diagnosis
in Engine Cooling. |
|
Engine
Mechanical
|
| • | Check for the following engine mechanical concerns: |
| - | Sticking or leaking valves |
| - | Excessive oil in the combustion chambers and leaking valve seals |
|
Additional
|
| • | Inspect the exhaust system for restrictions. |
| - | Inspect the exhaust system for damaged or collapsed pipes. |
| - | Inspect the mufflers for heat distress or internal failure. |
| - | Inspect for catalytic converter. |
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