Poor Fuel Economy

WARNING: This page is about a different car, the 2002 Ford Pickup and 2002 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Fuel consumption can be increased during stop-and-go driving, trailer towing, short-run operation, extended winter warm-up periods, improper tire inflation, high speed driving, improper axle ratio and aftermarket add-ons. Determine if these factors are the cause of poor fuel mileage before proceeding with diagnostic procedure.

Connect scan tool to Data Link Connector (DLC). Turn ignition on. Using scan tool, access PCM and select DPFEGR (if equipped), LONGFT1, LONGFT2 and VPWR PIDs from PID/DATA MONITOR & RECORD menu. See PIN VOLTAGE/PID VALUE CHARTS - TRUCKS article. DPFEGR PID value should be within .15 volt of Key On Engine Off (KOEO) value. If DPFEGR PID value is not as specified, check EGR. See TEST HE: EGR SYSTEM , step 100) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article. If LONGFT1 or LONGFT2 PID value is low (-20 percent), concentrate checks in areas that would cause engine to run rich. If LONGFT1 or LONGFT2 PID value is high (+20 percent), concentrate checks in areas that would cause engine to run lean. If VPWR PID voltage is not 10.5-17.0 volts, check charging system. See GENERATORS & REGULATORS - BLACKWOOD, EXPEDITION, F150 & NAVIGATOR article in STARTING & CHARGING SYSTEMS. If VPWR PID voltage is 10.5-17.0 volts but not within .5 volt of battery voltage, check battery supply to PCM power relay. Check VPWR circuit between PCM and PCM power relay, and PWR GND circuits to PCM. See WIRING DIAGRAMS article.
Check A/T Torque Converter Clutch (TCC) and/or TCC solenoid for proper operation. See FORD 4R70W DIAGNOSIS or FORD 4R100 DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.
Check PCV system. See TEST HG: PCV SYSTEM under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Check for correct PCM Vehicle Identification (VID) block information. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE under PROGRAMMING PCM in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article. Check for dragging brakes and repair as necessary. See DISC & DRUM - TRUCKS - EXCEPT VILLAGER article in BRAKES. Visually inspect Mass Air Flow (MAF) sensor for contamination.
Check cooling system for overheating. If cooling system is overheating, repair as necessary. See appropriate ELECTRIC COOLING FANS article in ENGINE COOLING.
Check transmission fluid level. Repair as necessary.
Check secondary ignition system. See TEST JB: SECONDARY IGNITION under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Check air intake system. See TEST HU: AIR INTAKE SYSTEM under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Check fuel delivery system. See TEST HC: FUEL DELIVERY SYSTEM under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - BI-FUEL article.
Check exhaust system for restriction. See TEST HF: CATALYST EFFICIENCY MONITOR & EXHAUST SYSTEMS under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.
Check engine mechanical condition. Check compression, camshaft, valve train components, etc. and repair as necessary. See appropriate article in ENGINES.
If no problems are indicated, return to SYMPTOM DIAGNOSIS to identify any additional symptoms or check for intermittent faults. See TEST Z: INTERMITTENT under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article.