Excessive Fuel Consumption

NOTE: Unless otherwise indicated, see SYSTEM & COMPONENT TESTING article for testing procedures.

Check ignition timing, idle speed and throttle position sensor adjustment. See ON-VEHICLE ADJUSTMENTS article.
Check battery and charging system. See GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS.
Check fuel injector circuits.
Check Idle Air Control Valve-Auxiliary Air Control (IACV-AAC) valve circuit.
Check ignition circuits.
Ensure cooling system is reaching normal operating temperature.
Check fuel pump circuit.
Check Exhaust Gas Recirculation (EGR) system.
Check fuel pressure regulator. See BASIC DIAGNOSTIC PROCEDURES article.
Check EVAP system.
Check PCV system.
Check Camshaft Position (CMP) sensor circuit.
Check Mass Airflow (MAF) sensor circuit.
Check Engine Coolant Temperature (ECT) sensor.
Check front Heated Oxygen Sensor (HO2S).
Check Throttle Position (TP) sensor circuit.
Check knock sensor circuit.
Check Vehicle Speed Sensor (VSS) circuit.
Check ECM power supply and ground circuits.
Check A/C system.
Check Park/Neutral Position (PNP) switch circuit.
Check engine mechanical condition.