GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1997 🢒 Sonoma Pickup - 4WD 🢒 Engine 🢒 Engine Controls - 4.3L 🢒 Poor Fuel Economy

Checks

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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 .
    • Check the air cleaner element (filter) for dirt or being plugged.
    • Visually (physically) check the vacuum hoses for splits, kinks, and proper connections as shown on the Vehicle Emission Control Information label.
    • Check the owner's driving habits for the following items:
    • The operation of the thermostatic air cleaner.
       - The A/C ON full time (Defroster mode ON)?
       - The tires for being at the correct air pressure.
       - Excessively heavy loads being carried?
       - The acceleration too much, too often?
    • 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 owner's manual.

Fuel System Checks
    • Check the fuel type, quality, and alcohol content. Refer to the Fuel System section.
    • Check the fuel pressure. Refer to Fuel System Pressure Test .

Ignition System Checks
    • Check the spark plugs. Remove the spark plugs and check for the following:
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
    • Check for an open Ignition Control (IC) circuit.
    • Check the ignition wires for the following items:
       - Cracking
       - Hardness
       - Proper connections
    • Check the Knock Sensor (KS) system operation. Refer to Knock Sensor (KS) System Diagnosis (Overview) .

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

Additional Checks
    • Check the transmission shift pattern. Refer to the Transmission Controls section.
    • Check for Torque Converter Clutch (TCC) operation. Refer to Torque Converter Clutch Solenoidin Automatic Transmission.
    • Check for proper calibration of the speedometer.
    • Check for dragging brakes. Refer to Section 5 of the appropriate service manual.