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.
California Models (Over 10,000 GVW)
Under normal vacuum conditions, metering valve is held open by a spring on vacuum side of diaphragm. This allows air from engine to pass into exhaust manifold. During deceleration (very high vacuum), vacuum is applied to diaphragm to overcome spring tension, closing metering valve momentarily. During closed metering valve, air is diverted to air cleaner or silencer. See Fig 1 .
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.