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 MANUALSMERCURY1991TRACER BASE, 4D SEDAN, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 5 (ENGINE CONTROLS - SYSTEM/COMPONENT TESTS - EEC-IV)EMISSION SYSTEMS & SUB-SYSTEMSAIR INJECTIONAIR CHECK VALVE
1991 Mercury Tracer Base, 4D Sedan, Automatic
Air Check Valve
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Air Check Valve
WARNING: This page does not describe the selected car, but rather 15 other vehicles, including the 1993 Mercury Tracer, 1993 Mercury Topaz, 1993 Mercury Sable, 1993 Mercury Grand Marquis, and 1993 Mercury Cougar. However, it is still accessible from the selected car via links, so may be relevant.
- Visually inspect thermactor hoses, tubes, control valves and check valves for leaks which may be due to backflow of exhaust gases. If holes are found and/or traces of exhaust gas products are present, replace check valve.
- Check valve should allow free flow of air in direction of arrow only. See Fig 1. Valves should check or block free flow of exhaust gas air in opposite direction.
- If air does not flow as indicated or if exhaust gas backflows opposite of direction of arrow in illustration, replace check valve.
RENDER: 1.0x
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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.