Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSFORD1991TAURUS L, 4D SEDAN, 3.8 4REPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - SYSTEM/COMPONENT TESTS - 3.8LEMISSION SYSTEMS & SUB-SYSTEMSAIR INJECTIONVACUUM CONTROL VALVE (VCV)
1991 Ford Taurus L, 4D Sedan, 3.8 4
Vacuum Control Valve (VCV)
1991 Ford Taurus L, 4D Sedan, 3.8 4SECTION Vacuum Control Valve (VCV)
- A 2-port valve may be in open or closed position when engine is cold, but should reverse when engine is warmed to operating temperature.
- For 3-port valves, with a cold engine, passage "A" to "B" should be closed and passage "A" to "C" should be open. See Fig 1 . With engine at normal operating temperature, the VCV should be open between "A" and "B" and closed between "A" and "C".
- For the 4-port valve, check "A1" to "B1" and "A2" to "B2" separately. See Fig 1 . A 4-port valve may be in open or closed position when engine is cold, but should reverse when engine is warmed to operating temperature. If these conditions are not met, replace the valve.
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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.