Poor Fuel Economy

Inspections	Action
DEFINITION: Fuel economy, as measured by an actual road test, is noticeably lower than expected.
Preliminary	Refer to Symptoms - Engine Controls . Inspect the air cleaner element, or the 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. Discuss the driving habits with the owner for the following items: The A/C is ON full time, or the defroster mode is ON The tires for being at the correct air pressure The wheel and tires are the correct size Excessively heavy loads being carried Aggressive driving habits Suggest to the owner to fill the fuel tank and to inspect the fuel economy. Suggest to the driver to refer to Important Facts on Fuel Economy in the owner manual.
Fuel System	Inspect the fuel type, quality, and alcohol content. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) . Test the fuel pressure. Refer to Fuel System Diagnosis .
Ignition System	Inspect the spark plugs. Remove the spark plugs and check for the following: Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . Inspect for an open ignition control (IC) circuit. Inspect the knock sensor (KS) system operation.
Cooling System	Inspect the engine coolant level. Inspect the engine thermostat for always being open or for the wrong heat range.
Additional	Inspect the transmission shift pattern. Refer to Symptoms - Automatic Transmission in Automatic Transmission - 4L60-E. Inspect the torque converter clutch (TCC) operation. Refer to Torque Converter Diagnosis Procedure in Automatic Transmission - 4L60-E. Inspect for proper calibration of the speedometer. Inspect for dragging brakes. Refer to Diagnostic Starting Point - Hydraulic Brakes in Hydraulic Brakes.