Chart 15-Poor Fuel Economy

NOTE: Fuel consumption increases drastically in city driving, short-run operation, stop-and-go driving, trailer towing, extended winter warm-up periods, etc. Determine if these are factors are the cause of poor fuel mileage before proceeding with diagnostic procedure.

DIAGNOSTIC CHART 15-POOR FUEL ECONOMY

System & Component(s)	Reference
FUEL/THROTTLE BODY Fuel Pressure Regulator Fuel Return Line Blocked	Perform a visual inspection. See FUEL SYSTEMS in I - SYS/COMP TESTS article.
AIR INTAKE SYSTEM Air Cleaner Duct & Element	See I - SYS/COMP TESTS article.
IGNITION Scope Engine For: Spark Plugs, Wires, Coil, etc. Ignition Timing	See IGNITIONS SYSTEMS in I - SYS/ COMP TESTS article.
EEC EEC-IV Quick Test	See TESTS W/CODES article.
COOLING Thermostat	Check cooling system.
FACTORS EXTERNAL TO THE ENGINE Tire Pressure Clutch Operation Converter Clutch Override Automatic Transmission Shift Pattern and Fluid Level Brake Drag Exhaust System Speedometer/Odometer Gear Ratio Axle Ration Vehicle Load Road and Weather Conditions Aftermarket Add Ons	Perform a manual & visual inspection.
BASE TRANSMISSION (A/T WITH OVERDRIVE) Converter Clutch Control Components Modulated Converter Clutch Control Solenoid	See TESTS W/CODES article.
EGR Valve Operation	See I - SYS/COMP TESTS article.