Poor Fuel Economy

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.(Larger than standard tires will cause odometer readings to be incorrect, and that may cause fuel economy to appear poor when it is actually normal.)

1. Was the "On-Board Diagnostic (OBD) System Check" performed?

[YES] Go to Step 2.
[NO] Go to OBD System Check. Initial Inspection

2. a. Perform a bulletin search.
b. If a bulletin that addresses the symptom is found, correct the condition as instructed in the bulletin.
c. Was a bulletin found that addresses the symptom?

[YES] Verify repair.
[NO] Go to Step 3.

3. Was a visual/physical check performed?

[YES] Go to Step 4.
[NO] Go to Visual/Physical Check. Visual/Physical Check

4. Check owner's driving habits:
- Is the A/C "ON" full time (defroster mode "ON")?
- Are tires at the correct pressure?
- Are excessively heavy loads being carried?
- Is acceleration too much, too often?

[YES] Go to Step 5.
[NO] Go to Step 6.

5. a. Review the items in Step 4 with the customer and advise as necessary.
b. Is the action complete?

[YES] System OK.

6. a. Visually/physically check:
- Vacuum hoses for splits, kinks, and improper connections and routing as shown on the "Vehicle Emission Control Information" label.
b. If a problem is found, repair as necessary.
c. Was a problem found?

[YES] Verify repair.
[NO] Go to Step 7.

7. a. Remove and check the air filter element for dirt or for restrictions.
b. If a problem is found, repair as necessary.
c. Was a problem found?

[YES] Verify repair.
[NO] Go to Step 8.

8. a. Remove the spark plugs and check for gas or oil fouling, cracks, wear, improper gap, burned electrodes of heavy deposits.

NOTE: If spark plugs are fouled, the cause of fouling must be determined before replacing the spark plugs.

b. If a problem is found, repair as necessary.
c. Was a problem found?

[YES] Verify repair.
[NO] Go to Step 9.

9. a. Check for low engine coolant level.
b. If a problem is found, repair as necessary.
c. Was a problem found?

[YES] Verify repair.
[NO] Go to Step 10.

10. a. Check for an incorrect or faulty engine thermostat.
b. If a problem is found, repair as necessary.
c. Was a problem found?

[YES] Verify repair.
[NO] Go to Step 11.

11. a. Check for low engine compression.
b. If a problem is found, repair as necessary.
c. Was a problem found?

[YES] Verify repair.
[NO] Go to Step 12.

12. a. Check the Torque Converter Clutch (TCC) operation.
b. If a problem is found, repair as necessary.
c. Was a problem found?

[YES] Verify repair.
[NO] Go to Step 13.

13. a. Check the exhaust system for possible restriction:
- Inspect the exhaust system for damaged or collapsed pipes.
- Inspect the muffler for heat distress or possible internal failure.
- Check for a possible plugged three-way catalytic converter by checking the exhaust system back pressure. Refer to Restricted Exhaust System Check.
b. If a problem is found, repair as necessary.
c. Was a problem found?

[YES] Verify repair.
[NO] Go to Step 14.

14. a. Check for proper calibration of the speedometer.
b. Does the speed indicated on the speedometer closely match the vehicle speed displayed on the scan tool?

[YES] Go to Step 16.
[NO] Go to Step 15.

15. a. Diagnose and repair an inaccurate speedometer condition as necessary.
b. Was a problem found?

[YES] Verify repair.

16. a. Check the air intake system and the crankcase for air leaks.
b. If a problem is found, repair as necessary.
c. Was a problem found?

[YES] Verify repair.
[NO] Go to Step 17.

17. a. Review all diagnostic procedures within this table.
b. If all procedures have been completed and no malfunctions have been found, review/inspect the following:
- Visual/physical inspection.
- Scan tool data.
- Freeze Frame data/Failure Records buffer.
- All electrical connections within a suspected circuit and/or system.
c. If a problem is found, repair as necessary.
d. Was a problem found?

[YES] Verify repair.
[NO] Go to Step 18.

18. a. Perform the procedure in Fuel System Pressure Test.
b. Was the fuel pressure normal?

[YES] Contact Technical Assistance.
[NO] Verify repair.