1991 Mercury Cougar LS, 3.8 4FACTORY OEM SERVICE PROCEDURE

Air Supply Control Valve

  1. Disconnect air supply hose at inlet. Accelerate engine to 1500 RPM and verify presence of airflow in hose. Reconnect air supply hose to valve inlet.
  2. Disconnect air supply hoses at outlets "A" and "B". See Fig 1 . Remove vacuum line at vacuum nipple. Accelerate engine to 1500 RPM. Airflow should be heard and felt at outlet "B" with little or no airflow at outlet "A".
    Fig 1: Air Supply Control Valve
    G90F14329Courtesy of FORD MOTOR CO.
  3. Connect a vacuum line from manifold vacuum fitting to air supply control valve vacuum nipple. Accelerate engine to 1500 RPM. Airflow should be heard and felt at outlet "A" with little or no airflow at outlet "B".
  4. If valve does not meet above conditions, replace valve. If airflow operates as described in steps 1), 2) and 3), valve is okay. Reinstall hoses and clamps.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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