Poor Fuel Economy

Definition: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, the economy is noticeably lower than it was on this vehicle at one time, as previously shown by an actual road test.

Preliminary Checks

^ Refer to "Important Preliminary Checks." Testing and Inspection

^ Check the air cleaner element (filter) for dirt or for being plugged.

^ Visually (physically) check: Vacuum hoses for splits, kinks, and proper connections as shown on "Vehicle Emission Control Information" label.

^ Check owner's driving habits:

- Is the A/C "ON" full time (Defroster mode "ON")?

- Check the tires for being at the correct pressure?

- Are exceedingly heavy loads being carried?

- Is the acceleration too much, too often?

- Suggest to the owner to fill the fuel tank and recheck the fuel economy.

Fuel System Checks

^ Check the fuel type, quality and alcohol content.

^ Check the fuel pressure. Refer to "Table A-7B." Table A-7B Fuel System Diagnosis (Fuel Pressure Check)

Ignition System Checks

^ Check the spark plugs for the following:

- Terminal screw - bent, loose (rotate and pull)

- Ceramic Insulator - cracks, tracking, deposits (red or black dust)

- Tip Insulator - cracks, tracking, deposits (oil, carbon, glazing, fuel additive), loose (rattles)

- Center electrode - loose (wiggles side to side)

- Platinum pads - missing, wear, gap size (too large or too small)

^ Check the ignition wires for cracking, hardness, and proper connections.

^ Check the Knock Sensor (KS) system operation.

^ Check the ignition timing.

Cooling System Checks

^ Check the engine coolant level.

^ Check the engine thermostat for always being open or for the wrong heat range. Refer to the appropriate service manual.

Additional Checks

^ Check the transmission shift pattern.

^ Check for the proper calibration of speedometer.

^ Check for dragging brakes. Refer to the appropriate service manual.