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Poor Fuel Economy Symptom

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

POOR FUEL ECONOMY SYMPTOM

Step Action Values Yes No
1 Was the "On-Board Diagnostic (OBDII) System Check" performed? - Go to Step 2 Go to On-Board Diagnostic (OBD-II) System Check
2
  1. Perform a bulletin search.
  2. If a bulletin that addresses the symptom is found, correct the condition as instructed in the bulletin. Was a bulletin found that addresses the symptom?
 - Verify repair Go to Step 3
3 Was a visual/physical check performed? - Go to Step 4 Go to VISUAL/PHYSICAL CHECK 
4 Check owner's driving habits.
  1. Is the A/C "ON" full time (defroster mode "ON")?
  2. Are tires at the correct pressure?
  3. Are excessively heavy loads being carried?
  4. Is acceleration too much, too often?
  5. Was a problem found?
 - Go to Step 5 Go to Step 6
5 Review the items in Step 4 with the customer and advise as necessary.
Is the action complete?		 - System OK -
6
  1. Visually/physically check: Vacuum hoses for splits, kinks, and improper connections and routing as shown on the "Vehicle Emission Control Information" label.
  2. If a problem is found, repair as necessary.
Was a problem found?		 - Verify repair Go to Step 7
7
  1. Remove and check the air filter element for dirt or for restrictions. Refer to Air Intake System.
  2. Replace the air filter element if necessary.
Was a repair required?		 - Verify repair Go to Step 8
8
  1. Remove spark plugs, and check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits.
    1. Check for Knock Sensor and Ignition Coil.
    NOTE: If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.
  2. If a problem is found, repair as necessary.
Was a problem found?		 - Verify repair Go to Step 9
9
  1. Check for low engine coolant level. Refer to ENGINE COOLING (6VE1-DI 3.5L) .
  2. If a problem is found, repair as necessary.
Was a problem found?		 - Verify repair Go to Step 10
10
  1. Check for an incorrect or faulty engine thermostat. Refer to ENGINE COOLING (6VE1-DI 3.5L) .
  2. If a problem is found, repair as necessary.
Was a problem found?		 - Verify repair Go to Step 11
11 Perform the procedure in Fuel System Check (High, Low).
Was the fuel pressure normal?		 - Verify repair Go to Step 12
12
  1. Check for VVT, VIM and Knock sensor function.
  2. If a problem is found, repair as necessary.
Was a problem found?		 - Verify repair Go to Step 13
13
  1. Check for low engine compression. Refer to ENGINE MECHANICAL (6VE1-DI - 3.5L) .
  2. If a problem is found, repair as necessary.
Was a problem found?		 - Verify repair Go to Step 14
14
  1. Check the TCC operation. Refer to TRANSMISSION CONTROL SYSTEM .
  2. If a problem is found, repair as necessary.
Was a problem found?		 - Verify repair Go to Step 15
15
  1. Check the exhaust system for possible restriction:
    1. Inspect the exhaust system for damaged or collapsed pipes.
    2. Inspect the muffler for heat distress or possible internal failure.
    3. Check for a possible plugged three-way catalytic converter by checking The exhaust system back pressure. Refer to Bank 1 Restricted Exhaust System Check  .
  2. If a problem is found, repair as necessary.
Was a problem found?		 - Verify repair Go to Step 16
16 Check for proper calibration of the speedometer.
Does the speed indicated on the speedometer closely match the vehicle speed displayed on the Tech 2?		 - Go to Step 18 Go to Step 17
17 Diagnose and repair an inaccurate speedometer condition as necessary. Refer to DTC P0502: Vehicle Speed Sensor Circuit No Signal .
Was a problem found?		 - Verify repair -
18
  1. Check the air intake system and the crankcase for air leaks. Refer to Air Intake System and Crankcase Ventilation System.
  2. If a problem is found, repair as necessary.
Was a problem found?		 - Verify repair Go to Step 19
19
  1. Review all diagnostic procedures within this table.
  2. When all procedures have been completed and no malfunctions have been found, review/inspect the following:
    1. Visual/physical inspection
    2. Tech 2 data
    3. Freeze Frame data/Failure Records buffer
    4. All connections within a suspected circuit and/or system.
  3. If a problem is found, repair as necessary.
Was a problem found?		 - Verify repair -
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