How to replace the idle speed controller on a Nissan Almera

The purpose and work of the IAC

The idle speed controller is an electric stepper motor

The K4M engine idle speed controller maintains the set engine idle speed with the throttle valve fully closed during its start-up, warm-up and when the load changes when auxiliary equipment is turned on

The regulator changes the amount of additional air supplied to the intake system in addition to the throttle, and is an electromechanical valve attached with two screws to the flange of the air filter housing.

The regulator valve seat and channels made in the filter flange form an additional air supply system, bypassing the throttle valve.

Idle speed regulator: 1 - housing; 2 - winding; 3 - lead screw; 4 - output; 5 - bearing; 6 - stator; 7 - rotor; 8 - spring; 9 - valve

The engine control unit, having processed the signals from the sensors, determines the need to open the regulator valve and transmits impulses to the regulator stator winding.

With each control pulse, the rotor rotates through a certain angle, moving the valve relative to the seat with the lead screw.

Additional air enters the intake pipe.

Determining the vacuum in the engine intake pipe, the control unit seeks to maintain it at a given level by periodically opening and closing the idle air control valve.

This makes it possible to supply a constant amount of additional air to maintain a constant idle speed.

By changing the opening and closing of the regulator valve, the control unit compensates for a significant increase or decrease in the amount of air supplied, caused by its suction through a leaky intake system or, conversely, by a clogged air filter.

The inclusion of additional units causes an increase in the load on the engine, accompanied by a decrease in the idling speed and a change in the vacuum in the intake pipe, which is also compensated by the control unit using the regulator.