Air entering the engine is monitored by the airflow sensor/HFM but how much air is controlled by the throttle body, which is connected to your gas pedal. Press the gas pedal down further and a butterfly valve opens wider in the throttle body. Cars from about 1999 use an electronic throttle valve and drive-by-wire electronics. On these models if the throttle body or throttle actuator fails the throttle will not open at all. Your engine's idle speed and smoothness are controlled either by the throttle body or with an idle control valve (ICV). The ICV is like an extra throttle body that allows a certain amount of air into the engine. Obviously any problems with either the throttle body or the ICV will affect engine drivability and smoothness. When looking for rough idle or poor throttle performance always check the
air intake boots for cracks or damage. Use our
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