Throttle Bodies

The throttle body controls airflow into the engine in a fuel injection system. It is mounted between the air cleaner and the intake manifold, and contains a butterfly valve, or plate, that operates according to accelerator pedal position. When the pedal is depressed, the valve opens allowing more air into the engine. At the same time various sensors signal the PCM (Powertrain Control Module) to correspondingly increase injector pulse width to boost fuel flow.

Many older vehicles are equipped with a simpler form of fuel injection called Throttle Body Injection (TBI). A TBI unit is a self-contained fuel injection assembly, with an integral pressure regulator and one or two injectors mounted over the throttle plates. Because it uses basically the same air filter and intake manifold as a carburetor, TBI was an inexpensive way to get the easier starting, better fuel economy and lower emissions provided by fuel injection.

Today most vehicles are equipped with multi-port fuel injection and fuel delivery is separate from the throttle body. In addition to the throttle plate, which is mounted to a shaft that passes through the housing, there is a port cast into the housing that bypasses the plate and is connected to the Idle Air Control (IAC) valve, which the PCM uses to regulate idle speed. A Throttle Position Sensor (TPS) is mounted to the end of the shaft and provides input to the PCM regarding the position of the throttle plate. The PCM uses this info along with input from sensors that measure airflow and/or vacuum to calculate fuel flow.

At one time the accelerator pedal actuated the throttle plate via mechanical linkage or cable. But that method has largely been supplanted by Electronic Throttle Control (ETC), colloquially known as “drive-by-wire”. This system eliminates mechanical problems like sticking and binding linkage, and allows throttle operation to be integrated with traction and stability control systems to increase driver safety. It includes multiple Accelerator Pedal Position (APP) sensors that signal pedal position to the PCM, and an electric motor on the throttle body that opens and closes the throttle blade in response to PCM commands.

Throttle bodies are generally reliable components, but on high mileage vehicles the shaft can wear, and dirt and deposit buildup can cause rough idle and stalling. Throttle bodies can often be cleaned with specialized cleaner, but some manufacturers do not recommend cleaning and replacement may be the only option. Components like ETC motors, TPS sensors and IAC valves can be replaced. TBI units can be resealed with new gaskets, much like a carburetor, plus we have complete replacement units, and individual components like injectors are available separately. Whatever your throttle body needs, we have the parts for the repair. We also offer performance parts. Replacing the OE throttle body with one of our performance units will not only further enhance airflow for a gain in horsepower, but you’ll also get better throttle response as well.