A throttle body is a computer-controlled or manually-operated butterfly valve located somewhere between an engine’s intake manifold and its air filter. It regulates the amount of air entering an engine to provide the motor with just the right volume needed at different engine loads. Too much air or its lack will lead to poor acceleration and overall engine performance as well as a variety of other problems.
When you push down or release the accelerator, the plate inside the throttle body opens or closes, changing the amount of air entering the intake manifold. Depending on the design of your throttle body, the movements of the plate are caused by either a cable connected to the gas pedal or a computer-operated motor.
Cable- or mechanically controlled throttle bodies had been popular till the middle of 2000s. They rely on a heavy, yet flexible cord that slides inside a plastic housing, moving the throttle body. This type of throttle body is prone to physical damage more often than its computer-controlled counterparts, which is why all new vehicles today come equipped with an electronic throttle body. These throttle bodies are driven by an electric motor operated by an engine control unit or powertrain control module. The computer compares data received from the throttle position sensor and the gas pedal position sensor, and then moves the throttle plate.
Electronic throttle bodies allow for more efficient air/fuel mixture control, resulting in better fuel economy and reduced emissions. They also made it possible to provide adaptive cruise control and some other smart functions.
A typical throttle body doesn’t require routine maintenance, however, it may fail or malfunction just like any other parts in a vehicle. If this happens, make sure you’re aware of the most common signs of a bad throttle body:
Illuminated check engine light
If you have an electronic throttle body, most likely your engine control unit monitors its performance. If it detects any problem, it will turn on the check engine light.
Lack of power and poor acceleration
A malfunctioning throttle body may not provide as much air as your engine needs at a specific moment. This will lead to reduced performance and poor acceleration.
A faulty throttle body may allow for too much or too low air entering the engine. Whichever happens, it will affect your idle speed.
“Limp-home” mode is activated
Your engine control unit always tries to protect the engine when something is going wrong with related systems or parts. For this reason, it may activate a “limp-home” mode by limiting engine power.
How to fix a bad throttle body
A throttle body should be serviced and diagnosed by a professional every 30,000 miles. If you notice any of the signs described above earlier, there could be several different scenarios. Your throttle body can just get dirty, which means you should clean it to fix the problem. If this doesn’t help, further diagnosis should be done to find the root of the troubles. In most cases, you’ll have to replace the throttle body or its components.