GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1999 🢒 Firefly (Canada) 🢒 Engine 🢒 Engine Controls - 1.3L 🢒 Poor Fuel Economy

Checks

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DEFINITION: Fuel economy, which is measured by an actual road test, is noticeably lower than expected. The fuel economy now is noticeably lower than previous fuel economy on this vehicle, which is shown by an actual road test.

Preliminary Checks
    • Refer to Symptoms .
    • Check the air cleaner element for dirt or for restrictions.
    • Visually inspect and/or physically inspect the vacuum hoses for splits, for kinks, and for correct connections which are shown on the label for Vehicle Emission Control Information.
    • Check the owner's driving habits for any of the following:
       - The defroster mode is ON all the time
       - The tires are not kept inflated correctly
       - Frequently carrying heavy loads
       - Heavy acceleration and high speeds are common.
       - Frequent short trips.
       - Extended periods of idling.
       - Driving on an unpaved road, on a dirt road, and on rough roads.
    • Suggest that the owner refill the fuel tank, and that the owner check the fuel economy again.

Fuel System Checks
    • Check the type, the quality, and the alcohol content of the fuel. Fuels with oxygen have lower energy and may deliver reduced fuel economy. Refer to Fuel System Specifications and Alcohol/Contaminants-in-Fuel Diagnosis .
    • Check for the correct fuel pressure. Refer to Fuel System Diagnosis .
    • Check the fuel injectors for correct operation. Perform the Fuel Injector Coil Test and the Fuel Injector Balance Test. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) and to Sequential Multiport Fuel Injector Balance Test .

Ignition System Checks
    • Check the spark plugs for any of the following conditions:
       - Wet plugs
       - A loose or bent terminal screw
       - A ceramic insulator that has cracks, has carbon tracking, or has deposits
       - A tip insulator that has cracks, has carbon tracking, has deposits, or is loose.
       - A center electrode that is loose
       - An incorrect spark plug gap
       - Refer to Spark Plug Visual Diagnosis in Engine Electrical.
    • Check the ignition wires for cracking, chafing, and loose connections.

Cooling System Checks
    • Check the engine coolant level.
    • Check the engine thermostat for always being open or for the wrong heat range. Refer to Thermostat Diagnosis in Engine Cooling.

Additional Checks
    • Check the transmission shift pattern and the clutch adjustment.
    • Check for dragging brakes.
    • Check for uneven tire wear or for premature tire wear. A suspension misalignment can cause a loss of fuel economy.
    • Check that the tires and the wheels are similar to OEM. Wide performance tires create more drag, and thinner tires can cause odometer differences.
    • Check for a green engine. Fuel economy may not be near expected levels until the engine is broken in for 4 800 -- 8 000 kilometers (3,000 - 5,000 miles).
    • Check the speedometer for correct calibration.
    • Check for add-on equipment such as luggage racks and such as carriers. Wind resistance can lower fuel economy.
    • Check the Service Bulletins for any updates or for any information.