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 , 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
|
| • | Ensure each injector harness is connected to the correct injector/cylinder. |
| • | Inspect for fuel in the pressure regulator vacuum hose. |
|
Sensor/System
|
| • | Monitor the 24X crankshaft position and camshaft position sensors
on scan tool. If both are not responding, test the sensor feed circuit. Both
sensors use a separate feed circuit but are internally connected to power.
Test all 24X and CMP sensor circuits for intermittents. Refer to
Testing for Intermittent Conditions and Poor Connections
in
Wiring Systems. |
| • | Monitor the 3X parameter on the scan tool. If the 3X is not responding,
inspect the 7X CKP sensor and circuits for intermittents. Inspect the IC circuit,
Bypass circuit, 3X Reference High Circuit, and the 3X Reference Low circuit
for intermittents. If these circuits become open, or shorted may not set a
DTC immediately, but are capable of causing driveability complaints. Refer
to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. |
| • | Inspect the air intake system and crankcase for air leaks. |
| • | Inspect for proper calibration of speedometer. Connect J 33431-B
signal generator to
VSS electrical connector. Ignition ON, tester ON and monitor the
speedometer. |
|
Ignition System
| 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 engine coolant level. |
| • | Inspect for incorrect or faulty engine thermostat. Refer to
Thermostat Diagnosis
in Engine Cooling. |
|
Engine Mechanical
|
| • | Inspect the engine mechanical for the following conditions: |
| - | Sticking or leaking valves |
| - | Excessive oil in combustion chamber or leaking valve seals |
| - | Low cylinder compression |
| • | Inspect the following components for incorrect basic engine
parts: |
|
Additional
|
| • | Inspect the exhaust system for possible restriction: |
| - | The exhaust system for damaged or collapsed pipes |
| - | The mufflers for heat distress or possible internal failure |
|
