How a Throttle Actuator and Throttle Bore Works

Featured on fuel injected vehicles a throttle body or actuator as they are referred to in new cars is used to control the engine speed via the accelerator pedal. Positioned at the upper portion of the intake manifold when the actuator is closed the engine will run at idle, and when fully open the engine will produce its maximum amount of power. A throttle actuator and throttle body are generally the same part, the throttle actuator is fully computerized (no cable) with no idle air control valve (IAC) and is sometimes referred to as a "drive-by-wire" system which uses an accelerator position sensor (APS) located at the pedal arm to control the actuator. As part of regular engine maintenance the throttle actuator must be serviced, usually at the same time a tune up is performed.

Here is a what a throttle actuator looks like on a 2019 vehicle which shows the air intake path, you can see the butterfly is closed, normally you cannot see this part when the air intake tube is installed.
throttle actuator

A throttle actuator is held to the intake manifold using three or four bolts sealed with a gasket. A computer wiring harness connector is plugged directly into the throttle actuator motor. A throttle position sensor (TPS) provides the throttle butterfly position data for the computer.
throttle actuator bolt wiring

Manufacturers will sometimes run hot engine coolant through the throttle bore to help heat up the intake air to improve fuel economy.
hot coolant lines

Older Vehicles

A throttle body is used on vehicles older than 2001-2005 (in general) and have a throttle cable connected to the gas pedal to open and close the actuator. This configuration uses an idle speed motor to control engine speed at idle via the computer program, there are no manual adjustments on a throttle bore, it is completely controlled by the engine computer. In the image below it shows what an idle air control valve looks like on a Toyota.
idle air control valve

Air bypass ports are designed onto the throttle bore (idle air valve removed) which facilitate engine idle speed adjustments from the computer.
throttle bore air ports


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