Inspection/Test
| 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
|
| • | Observe the owners driving habits. |
| - | Is the A/C ON full time, with the defroster mode ON? |
| - | Are the tires inflated to the correct pressure? |
| - | Are excessively heavy loads being carried? |
| - | Is the acceleration too much, or too often? |
|
Fuel System
|
| • | Ensure each injector harness is connected to the correct injector
and cylinder. |
| • | Inspect for fuel in the pressure regulator vacuum hose. |
|
Sensor/System
|
| • | Observe the 24X crankshaft position (CKP) sensor and the camshaft
position (CMP) sensor on the scan tool. If neither sensor is responding, check
the sensor feed circuit. Both sensors use a common feed circuit. |
| • | Inspect the air intake system and the crankcase for air leaks. |
| | Inspect the air intake ducts for being collapsing, damaged areas, looseness,
improper installation, or leaking, especially between the mass air flow
(MAF) sensor and the throttle body. |
| • | Inspect for the proper calibration of the speedometer. Connect
a J 33431-B
signal generator
to the electrical connector of the vehicle speed sensor (VSS) . Turn the
ignition and the tester ON and monitor the speedometer. |
|
Ignition System
|
| • | Test for the proper ignition voltage output using the following
procedure: |
| 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: |
| - | Check the coils for cracks, carbon tracking or arcing, or a resistance
value outside the specified range. |
Coil Resistance
5,000-8,000 ohms | - | Check the spark plug wires for signs of arcing, cross-firing,
cracks, carbon tracking, plug boot damage, pinching, improper routing, or
a resistance value outside the specified range. |
Spark Plug Wire Resistance
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 problem. The ignition voltage will arc to ground
when a secondary component is faulty.
|
| - | Test for a defective ignition 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 conditions: |
| - | 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. Refer to
Spark Plug Visual Diagnosis
in Engine Electrical. |
|
Engine Cooling System
|
| • | Inspect the engine coolant for the correct level. |
| • | Inspect for an incorrect or faulty engine thermostat. Refer to
Thermostat Diagnosis
in Engine Cooling. |
|
Engine Mechanical
|
| • | Inspect the engine for the following conditions: |
| - | An incorrect compression |
| - | Any sticking or leaking valves |
| - | Any worn camshaft lobes |
| - | An incorrect valve timing |
| - | Any broken valve springs |
| - | Any excessive oil in the combustion chambers and leaking valve
seals |
| • | Inspect for the following components for incorrect basic engine
parts: |
|
Additional
|
| • | Test the TCC operation. Refer to torque converter clutch (TCC)
in transaxle diagnosis. |
| • | 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 a plugged catalytic converter. |
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