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Idle Speed

  1. Start and warm engine to normal operating temperature (cooling fan comes on). Connect tachometer. Disconnect 2-wire Idle Air Control (IAC) valve connector. Ensure all accessories and cooling fan are off.
  2. Check idle speed (before ECM is reset). If necessary, adjust idle speed by turning idle adjusting screw. See Fig 1 . See IDLE SPEED SPECIFICATIONS  table.
  3. Turn ignition off. Reconnect 2-wire IAC connector. Remove BACK-UP fuse (Accord, Civic and Civic Del Sol) or CLOCK RADIO fuse (Prelude) from underhood relay box for 10 seconds to reset ECM. Restart engine.
  4. On Civic, Civic Del Sol and Prelude, check idle speed (after ECM reset) with all accessories off and transmission in Neutral or Park. On Accord, check idle speed (after ECM reset) with transmission in gear.
  5. On all models, idle engine for one minute with various accessories on, and check idle speed. Idle speed should be stable and within specification. See IDLE SPEED SPECIFICATIONS  table. If idle is not within specification, check vacuum hose connections. Check idle adjuster screw, fast idle valve and Idle Air Control (IAC) valve for proper operation.
  6. If idle components are okay, check MAP sensor, Electronic Load Detector (ELD), fuel injector circuit, A/C signal circuit, EGR system and lock-up control solenoid (if equipped) for proper operation. For component testing procedures, see appropriate G - TESTS W/ CODES and SYSTEM/COMPONENT TESTS articles in the ENGINE PERFORMANCE Section. On Civic VX there has been a revision as per TSB Number HSN-0894-02 dated August 1994. Idle engine for one minute with headlights (low) ON, and check idle speed.
    IDLE SPEED SPECIFICATIONS

    Application RPM
    Accord & Prelude
    Before ECM Reset (1) 500-600
    After ECM Reset (2)
    No Load 650-750
    Under Load 720-820
    Civic & Civic Del Sol
    Before ECM Reset (1) 370-470
    After ECM Reset (2)
    No Load
    A/T 650-750
    M/T
    Except D15Z1 M/T 620-720
    D15Z1 M/T 550-650
    Under Load
    Except D15Z1 M/T 700-800
    D15Z1 M/T 650-750
    (1) With Idle Air Control (IAC) valve disconnected, headlights and cooling fan off and transmission in Neutral or Park.
    (2) See IDLE SPEED  under IDLE SPEED & MIXTURE.
    Fig 1: Locating Idle Adjusting Screw (Accord Shown; Other Models Similar)
    G90G17117Courtesy of AMERICAN HONDA MOTOR CO., INC.
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