Excessive Fuel Consumption

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2003 Infiniti QX4, 2003 Infiniti Q45, 2003 Infiniti M45, 2003 Infiniti I35, and 2003 Infiniti G35. However, it is still accessible from the selected car via links, so may be relevant.

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

Check ignition timing and idle speed adjustment. See ON-VEHICLE ADJUSTMENTS article.
Check TP sensor adjustment (QX4 only). See ON-VEHICLE ADJUSTMENTS article.
Check fuel injector circuits.
Check Idle Air Control Valve-Auxiliary Air Control (IACV-AAC) valve circuit (QX4 only).
Check electric throttle control actuator (Except QX4).
Check ignition circuits.
Check ignition timing. See ON-VEHICLE ADJUSTMENTS article.
Check mass airflow sensor circuit.
Check front HO2S circuits.
Check engine coolant temperature sensor circuit.
Check TP sensor circuit.
Check fuel pump circuit.
Check ECM power and ground circuits.
Check A/C circuit.
Check vehicle speed sensor circuit.
Check knock sensor circuits.
Check for faulty ECM. See appropriate SELF-DIAGNOSTICS article.
Check park/neutral position switch circuit.
Check intake valve timing control solenoid valve circuit (Except I35 & QX4).
Check fuel pressure regulator. See BASIC DIAGNOSTIC PROCEDURES article.
Check EVAP system.
Check PCV system.
Check refrigerant pressure sensor circuit (Except I35 & QX4).