The throttle body is a device located in the engine compartment, between the intake manifold and air intake pipe. It is similar to the carburetor but does not regulate fuel flow. The throttle body monitors the amount of air that can flow into an engine’s combustion chamber. The most important and largest part inside the throttle body is its throttle plate. This plate has a butterfly valve, which rotates on the throttle shaft. When the throttle plate is rotated by the shaft the air flows in and out of the engine.
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 pressure is applied to the pedal, the valve opens allowing more air into the engine. At the same time various sensors signal the Powertrain Control Module (PCM) to correspondingly increase injector pulse width to boost fuel flow.
Many modern throttle bodies have spring loaded sensors and plastic gears that are not intended to be manipulated directly during any diagnostics or inspections. These components are controlled electronically or generate signals. It is best to let a mechanic use approved tests to diagnose the problem.
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.
