Circuit Description

The aim of the MTIA (Main Throttle Idle Actuator) is to control the idle speed with the throttle body itself. The throttle is motorized for low opening angle (0, 18°). The characteristics of the airflow are not the same for low and high opening angles. As a matter of fact, the gradient of the mass air flow function of TPS is lower for small angles that permits to be more precise during the idle speed control. Out of idle speed the throttle is actuated mechanically by a classical bowdencable.

The throttle position sensor (TPS) provides a voltage signal that changes in relation to the throttle plate angle. The signal voltage will vary from about 4.15~4.75V at idles to about 0.3~1.05V at wide-open throttle. The TPS is one of the most important inputs used by the ECM for fuel control and other functions such as idle, wide open throttle, deceleration enleanment, and acceleration enrichment.