A throttle body is an aluminum housing mounted near the top of an engine that meters the amount of air that enters the combustion chambers. The throttle body is located between the air intake (and engine air filter) and the intake manifold. Inside the throttle body is a butterfly valve (the “throttle plate”) that opens and closes in relation to the throttle (gas pedal) position. In the case of older vehicles, the valve was actuated directly by a cable coming from the gas pedal. Newer designs rely instead on an electronic signal, with no mechanical connection between the two.
Most engines rely on a single throttle body, although some larger engines feature a separate throttle body for each bank of cylinders.
The signs of a bad throttle body mirror problems with other components, such as a transmission malfunction, fuel system failure, or faulty throttle position sensor. Fortunately, most modern engines rely on a computer, the Engine Control Module, to communicate with electronic components, including the throttle position sensor that is attached to the throttle body. So, a diagnostic scan might reveal the condition of each component. But the throttle body itself might need to be replaced if you notice one or more of the following signs:
If the throttle body on your engine needs to be replaced, a technician will perform the following general steps:
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