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, defroster mode ON? |
| - | Are tires at correct pressure? |
| - | Are excessively heavy loads being carried? |
| - | Is acceleration too much, too often? |
|
Fuel
System
|
| • | Test for faulty fuel injectors. Refer to the following test procedures: |
| • | Ensure each injector harness is connected to the correct injector
and/or cylinder. |
| • | Inspect for fuel in the pressure regulator vacuum hose. |
|
Sensor/System
|
| • | Observe the 24X crankshaft position (CKP) and camshaft position
(CMP) sensors on the scan tool. If both are not responding, check the sensor
feed circuit. Both sensors use a common feed circuit. |
| • | Inspect the air intake system and crankcase for air leaks. |
| • | Inspect the air intake ducts for the following conditions: |
| - | Leaking conditions especially between the MAF sensor and
the throttle body |
| • | Inspect for proper calibration of speedometer. Connect a J 33431-B
signal generator to
the vehicle speed sensor (VSS) electrical connector. Ignition ON, 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
. 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
. A spark should be observed. |
| 5. | Repeat the above steps for each coil. |
| | 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.
|
| • | If spark is not present at the coils, inspect the following components
for the specified conditions: |
| - | Coils--Cracks, carbon tracking and/or arcing, or a resistance
value outside the specified range |
Coil Resistance
5000-8000 ohms (5K-8K ohms)
Spark Plug Wire Resistance
9868 ohms per meter (3000 ohms per foot)
| • | A resistance value outside the specified range |
| - | 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. Refer to
Spark Plug Inspection
. |
|
Engine
Cooling System
|
| • | Inspect the engine coolant level for 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: |
| - | Sticking or leaking valves |
| - | Excessive oil in combustion chamber due to leaking valve seals |
| • | Inspect the following components for incorrect basic engine parts: |
|
Additional
|
| • | Test torque converter clutch (TCC) operation. Refer to torque
converter clutch (TCC) in transaxle diagnosis. |
| • | Inspect the following components of the exhaust system for possible
restrictions: |
| - | Inspect for damaged or collapsed pipes. |
| - | Inspect the mufflers for heat distress or possible internal failure. |
| - | Test for possible plugged catalytic converter by testing the
exhaust system back pressure. |
|
