GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Safari - 4WD 🢒 Engine 🢒 Engine Controls - 4.3L 🢒 Poor Fuel Economy

Checks

Action

DEFINITION: Fuel economy, as measured by an actual road test, is noticeably lower than expected.

Preliminary Checks
    • Refer to Symptoms .
    • Inspect the air cleaner element (filter) for dirt or being plugged.
    • Visually and physically inspect the vacuum hoses for splits, kinks, and proper connections as shown on the Vehicle Emission Control Information label.
    • Verify the owners driving habits for the following items:
       - The A/C ON full time (defroster mode ON).
       - The tires for being at the correct air pressure.
       - Excessively heavy loads being carried.
       - Aggressive driving habits.
    • Suggest to the owner to fill the fuel tank and to recheck the fuel economy.
    • Suggest to the driver to refer to Important Facts on Fuel Economy in the owners manual.

Fuel System Checks
    • Inspect the fuel type, quality and alcohol content. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect the fuel pressure. Refer to Fuel System Diagnosis .

Ignition System Checks
    • Inspect the spark plugs. Remove the spark plugs and check for the following:
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
    • Inspect for an open ignition control (IC) circuit.
    • Inspect the ignition wires for the following items:
       - Cracking
       - Hardness
       - Proper connections
    • Inspect the knock sensor (KS) system operation.

Cooling System Checks
    • Inspect the engine coolant level.
    • Inspect the engine thermostat for always being open or for the wrong heat range.

Additional Checks
    • Inspect the transmission shift pattern. Refer to Torque Converter Diagnosis in Automatic Transmission.
    • Inspect for torque converter clutch (TCC) operation. Refer to Torque Converter Diagnosis in Automatic Transmission.
    • Inspect for proper calibration of the speedometer.
    • Inspect for dragging brakes.