Inspections
| Action
|
DEFINITION: Fuel economy, as measured by an actual road test, is noticeably
lower than expected. Also, fuel economy is noticeably lower than the economy was
on this vehicle at one time, as previously shown by an actual road test.
|
Preliminary
|
• | Discuss the following with the owner that may effect fuel economy: |
- | Is the A/C ON or the Defroster mode ON full time? |
- | Are the tires at the correct pressure? |
- | Are the wheels and tires the correct size? |
- | Are there excessively heavy loads being carried? |
- | Is the acceleration rate too much, too often? |
Remove the air filter element and inspect for dirt or for restrictions. Refer
to
Air Cleaner Element Replacement
. Replace
as necessary.
|
Fuel System
|
• | Discuss with the owner the type, quality, and alcohol content of the fuel.
Oxygenated fuels have lower energy and may deliver reduced fuel economy. Refer to
Alcohol/Contaminants-in-Fuel Diagnosis
. |
• | Inspect that each fuel injector harness is connected to the correct fuel
injector and cylinder. Relocate the fuel injector harnesses as necessary. |
|
Sensor/System
|
• | Inspect for the following that may cause the engine to run rich: |
Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section. - | Water intrusion in the heated oxygen sensor (HO2S) connector |
- | Purging of a saturated evaporative emission (EVAP) canister |
- | Vacuum hoses that are split, kinked, or improperly connected |
- | An air intake duct that is collapsed or restricted |
• | Inspect the air intake system and crankcase for air leaks. |
• | Monitor the knock sensor (KS) system for excessive spark retard activity
with a scan tool. Refer to
Scan Tool Data Definitions
. |
|
Ignition System
|
• | In order to properly inspect the spark plugs or to correct a condition,
refer to the following procedures: |
• | Inspect for proper secondary ignition voltage output with the J 26792
HEI Spark Tester. |
• | An improper spark plug gap will cause a driveability condition. Gap the
spark plugs using a wire gage gap tool. |
• | If the spark plugs are found to be fouled, determine the cause before
replacing the spark plugs. |
• | Monitor the Misfire Current Counters while driving the vehicle in the
conditions that the symptom occurred. If a misfiring cylinder can be located, use
the DTC P0300 table for diagnosis. Refer to
DTC P0300
. |
|
Engine Cooling System
|
• | Inspect the engine coolant level for being low. Refer to
Loss of Coolant
in Engine Cooling. |
• | Inspect the engine thermostat for proper operation and for the correct
heat range. Refer to
Thermostat Diagnosis
in Engine Cooling. |
|
Engine Mechanical
|
• | Inspect engine mechanical for the following: |
- | Sticking or leaking valves |
- | Excessive oil in combustion chamber or leaking valve seals. |
- | For more information, refer to one or more of the following procedures in Engine
Mechanical: |
• | For incorrect, worn, or damaged basic engine parts, inspect the following: |
|
Additional Inspections
|
• | Visually and physically inspect the vacuum hoses for splits, kinks, and
proper connections and routing as shown on the Vehicle Emission Control Information
label. |
• | Inspect the transmission torque converter clutch (TCC) operation. The
scan tool should indicate an RPM drop when the system commands the TCC ON. |
• | Inspect the exhaust system for a possible restriction. Inspect for the
following: |
- | The exhaust system for damaged or collapsed pipes |
- | The mufflers for heat distress or possible internal failure |
• | Inspect the brake system for dragging or improper operation. Refer to
Brakes Drag
in Hydraulic Brakes. Verify that the vehicle
operator does not drive with a foot on the brake pedal. |
|