What Is a Throttle Body

Educational  ·  February 14, 2022

What Is a Throttle Body

There are at least two main types of engines – electric and internal combustion engines (or ICE). While an electric engine relies on electricity produced by a motor, an ICE produces power using fuel and air in a process called combustion. 

For the combustion of fuel to take place and power the engine, there must not only be fuel but also oxygen. That’s why an ICE needs an air intake system, wherein the throttle body plays a primary role. 

Functions of a Throttle Body

The throttle body, which sits between the manifold and the air filter, has two functions. 

  1. It regulates the amount of air inflow – The throttle plate opening regulates the amount of air flowing into the engine and ensure there’s adequate supply. The wider the throttle plate opens, the more air it takes in. 
  2. It controls the temperature of air inflow – The throttle body uses the engine coolant line to cool or warm the air as needed. Air has a specific density at a given temperature, which facilitates fuel injection at the right air-fuel ratio. 

How Does a Throttle Body Work?

A throttle body performs its functions via two air inlets.

  1. Primary inlet – This is the central air intake that starts working when the driver steps on the accelerator or gas pedal. As the accelerator is pressed, the throttle plate (aka the butterfly) opens to allow more air into the engine. The harder the driver pushes the accelerator, the wider the inlet opens. As the gas pedal is released, the plate closes, halting the flow of air into the combustion chamber. The throttle body communicates with the accelerator via the throttle cable (for older cars) or electronic sensors (for more modern vehicles). 
  2. Secondary air intake – this is a smaller bypass that allows air in when the engine is idling. It has the Idle Air Control Valve (IACV), which is a solenoid-driven valve used by the ECU to control air inflow, allowing the engine to idle. During idling, the throttle plate is shut, letting in no air. Without the bypass, combustion would stop, making it impossible for idling to happen.

How Is a Throttle Body Mounted?

Throttle bodies can be configured as follows:

  1. Single throttle body per engine – this is common in standard vehicles where one throttle body serves the whole engine.
  2. Multiple throttle bodies per engine – where more than one throttle body is employed and are linked together to function simultaneously.
  3. Individual throttle bodies (ITBs) – this is standard in higher-performance cars and motorcycles where each combustion cylinder has its separate throttle body.

Different Types of Throttle Bodies 

Throttle bodies can be classified into three depending on how the throttle body communicates with the accelerator or how the accelerator controls it. 

  1. Mechanically controlled – the throttle body is controlled using a throttle cable that connects to the accelerator
  2. Mechanically/electronically controlled – the throttle body is semi-controlled by a cable, and sensors play a vital role in controlling the opening and closing of the throttle plate.
  3. Electronically controlled – the control of the throttle body is primarily by sensors (Fly by Wire)

What Are the Common Issues with Throttle Bodies? 

The common problems associated with throttle bodies include:

  1. Faulty temperature sensor
  2. Vacuum pipe leak 
  3. Carbon build-up 
  4. Breaking of the drawback spring that crosses the butterfly valve
  5. Dirt build-up inside the housing
  6. Corrosion of the throttle body part
  7. Loss of the primary throttle setting

Symptoms of a Problematic Throttle Body

When the throttle body is flawed, distinct signs appear, including:

  1. Rough idling and idle surges – caused by irregular air intake
  2. Dashboard check engine light – the car sensors will send a warning that there is an issue with an engine component
  3. Poor engine performance – the vehicle loses power due to inadequate air supply
  4. Jumping RPM – likely caused by faulty wiring or vacuum leaks
  5. Engine stalling – the engine stalls despite the vehicle having fuel and a fully-charged battery
  6. Fuel inefficiency – a noticeable increase in fuel consumption
  7. Acceleration issues – annoying surge in speed when accelerating or hesitation while pushing on the accelerator
  8. Jerking when you engage the gear – changing the gear becomes difficult as the vehicle lacks the power to drive in the next higher gear.

If your vehicle starts showing the above signs, it’s time to have the throttle body checked. At CarPart AU we link you to the best service providers and the leading car part dealers in Australia. Visit our site for more details now!

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