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.
Throttle Positioner System: Description
The Throttle Positioner (TP) system controls exhaust emissions during deceleration by holding throttle plate at an above-idle position during deceleration. This aids in complete burning of the air/fuel mixture.
System consists of Throttle Positioner (TP), Vacuum Transmitting Valve (VTV), Thermostatic Vacuum Switching Valve (TVSV), Vacuum Switching Valve (VSV) and jet assembly. Components may vary due to model application. The TP may be a single or a double diaphragm. System is controlled by engine vacuum. Engine operating temperature is used to control the various components. See Fig 1 and Fig 2 .
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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.