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.
Deceleration Control System: Operation
Manifold vacuum is routed through a solenoid vacuum valve, which is normally closed, to the vacuum throttle positioner (modulator).
Power is available to solenoid vacuum valve through an electronic sensor, but the sensor ground circuit is open. When engine speed is higher than a predetermined RPM setting, a signal is sent to the solenoid, which allows manifold vacuum to activate the throttle positioner.
Vacuum pulls the throttle positioner diaphragm, which pushes the throttle to high idle position during deceleration.
Use the Manual With the Right Hardware
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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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