9000 L4-2290cc 2.3L DOHC Turbo EFI (1992)
Idle Speed/Throttle Actuator - Electronic: Description and Operation
Idle Air Control Valve (IAC valve)
Description
This idle air control valve differs from the LH 2.2 valve in that the reversible motor is replaced by a solenoid. The coil (2) receives pulse signals from
the control module. When activated, the coil overcomes a mechanical spring (5) that keeps the valve closed. This allows a specific volume of air to
flow past the throttle butterfly in the intake manifold.
In the event of a fault, the opening pulses terminate and the spring (5) pulls the valve to the end position. The air flow through the valve in this
position (Limp Home) is greater than during normal operating conditions. This gives an idle speed of 1,200 - 1,500 rpm.
The Limp Home function is activated when a fault arises in the IAC system, such as might be caused by a loose cable.
During deceleration when the throttle butterfly is fully closed (braking), the valve is controlled by the control module so that extra air can flow past the
throttle butterfly. This is to ensure complete combustion of any injected fuel. This function replaces the dashpot function in the LH 2.2 system.
Idle speed control in the LH 2.4.1 system has been further improved. This has been achieved by the addition of vehicle speed information to the
control module's calculations. The signal is obtained from the speedometer.
As long as the speed of the car exceeds about 6-8 km(h, engine speed will be higher than idle speed but will drop to idle speed when this speed limit is
no longer reached.
As a result, braking to a standstill is extremely smooth.
