The idle speed regulator is a simple stepper motor with a spring-loaded cone needle. At idle speed, air enters the motor by changing the flow capacity of the channel through which it enters. This is known here: https://scrap4cash.com/blogs/the-top-5-most-expensive-car-repairs/.
The volume of the air entering through the flap is monitored by an air flow sensor. The controller arranges the flow of petrol through the injectors into the engine. The crankshaft position sensor informs the controller about the engine rpm. On the basis of these data the idle speed regulator is controlled to increase or decrease air supply.
If the engine is warmed up, the controller keeps the idling speed.
In some cases, the controller increases revolutions on the unheated engine, which leads to increase of crankshaft revolutions. As a result, it is possible to instantly drive the car without warming up the engine.
The idle speed controller is attached to the choke with two bolts. On some cars, their heads are drilled, or they sit on the varnish. This makes it difficult to remove the regulator to clean the channel or install a new unit. As a result, you have to remove the entire throttle.
The idle speed regulator is an actuator type device, so if it malfunctions, no error is displayed on the car’s onboard computer. That’s why you need to watch closely for indirect signs that indicate a defect in the work of this mechanism. These include:
spontaneous rise or fall of engine rpm;
absence of high revolutions at cold start;
rpm spikes in idle mode;
disconnection of the engine when switching off the gear and so on.
To repair the regulator disassemble it by first disconnecting the 4-pin connector and removing the 2 fixing bolts. Installation is done in the same way, but in the opposite order. The main thing is to apply engine oil to the o-ring on the flange. And don’t forget to make sure that there is exactly 23 mm between the point of the cone needle and the flange.