Idle Air Control System

IDLE AIR CONTROL SYSTEM

Description

Operation
- The PCM carries out idle air control through the following modes.
i. Deceleration mode
ii. Closed loop control mode

Deceleration mode (i.e. closed or partially closed throttle)
During deceleration the PCM enables the IAC to adjust airflow to the throttle body to prevent engine stalling.

Closed loop control mode
- The following conditions must be met for idle air control in closed loop control mode.
i. The vehicle speed is below 4 km/h {2.5 mph}.
ii. The PCM determines the neutral condition based on the input by the neutral/clutch switch. (MTX only)

- The purpose of closed loop control mode is to maintain engine stability when idle through feedback control.

Adoptive air compensation




- The PCM memorizes the idle air trim level required to maintain the target engine speed. When the following conditions exist, the PCM prohibits adaptive air compensation.
i. During closed loop control mode.
ii. During no load condition (Neutral [MTX], N position [ATX]) instead of the closed loop control. (When changes of engine speed are above specification)
iii. When it does not meet condition (1) or (2) above, and the charging efficiency is below the specified value.

- When the idle air trim correction is above the specified value, the PCM judges the malfunction in the idle air control system, and stores a DTC.
- If the keep Alive RAM has been reset, the idle air trim learning correction is also cleared, the engine must idle for 15 minutes at each of the following four separated modes to learn the new idle air trim




Target engine speed
- The optimum engine speed at idle as shown.

Block Diagram: