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 MANUALSJEEP1987WRANGLER LAREDO, 4.2 C, STANDARDREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMEGR FUNCTION TESTINGTESTINGTHERMAL VACUUM SWITCH (TVS)
1987 Jeep Wrangler Laredo, 4.2 C, Standard
Thermal Vacuum Switch (TVS)
1987 Jeep Wrangler Laredo, 4.2 C, StandardSECTION Thermal Vacuum Switch (TVS)
- With the air cleaner temperature below 40°F (-4°C), disconnect vacuum hoses from TVS and connect vacuum source to large outlet.
- Apply vacuum to TVS. TVS should hold vacuum. If not, replace TVS.
- Start engine and warm air cleaner to 55°F (13°C), or greater. TVS should not hold vacuum. If it does, replace TVS.
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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.