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Home >> Honda >> 1990 >> Prelude 2.0 S, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests - CARBURETED >> Fuel System >> Fuel Control >> Primary Slow Mixture Cut-Off Solenoid Valves

Primary Slow Mixture Cut-Off Solenoid Valves

  1. Turn ignition switch to ON position and check for a clicking sound at each solenoid valve. See Fig 1 . If solenoid valves do not click, go to step 4). If each solenoid valve clicks, go to next step.
  2. Start engine and warm to normal operating temperature (cooling fan comes on). Raise and support front of vehicle. Block rear wheels and set parking brake. Place transmission in 2nd gear or in "2" position, accelerate to 4000 RPM and then suddenly release throttle. Check for clicking sound at each solenoid valve while decelerating from greater than 12 MPH and 4000 RPM. If solenoid valves clicks, valve is okay. If solenoid valves do not click, go to next step.
  3. Turn ignition off and connect ECU Test Harness (07LAJ-PT30100 ) between ECU and main harness connector. See Figure . Start engine and measure voltage between terminals A21 (positive) and A26 (negative) See Figure during deceleration from greater than 12 MPH and 4000 RPM. If voltage momentarily ceases during deceleration, replace solenoid valve. If voltage does not cease, observe CHECK ENGINE light and self-diagnosis LED indicator. If okay, substitute a known good ECU and retest. If symptom goes away, replace original ECU.
  4. If solenoid valve did not click, turn ignition off. Connect ECU Test Harness between ECU and main connector. See Figure . Turn ignition switch to ON position and measure voltage between ECU terminals A21 (positive) and A26 (negative). See Figure . If battery voltage is present, go to step 5). If battery voltage is not present, observe CHECK ENGINE light and self-diagnosis LED indicator. If okay, substitute a known good ECU and retest. If symptom goes away, replace original ECU.
  5. If battery voltage was present, check for open or short in Black/Yellow wire between solenoid valve and ECU terminal A21. If wire is okay, check right solenoid valve (on right carburetor) and replace solenoid valve if necessary. See Fig 1 . Inspect for open or short in Black wire between left solenoid (on left carburetor) and ground, and/or check and replace left solenoid valve (if necessary).
    Fig 1: Locating Primary Slow Mixture Cut-Off Solenoid Valves
    G117913Courtesy of AMERICAN HONDA MOTOR CO., INC.
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