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Your Idle Control Valve (Idle Air Control Valve) worn out? » Read more about common malfunctions • Repair • Replacement manual
Smooth idling with the idling actuator
The idling actuator is a small component that is important to the operation of the engine. It regulates the car's RPM in such a way, that the engine doesn't stall despite the driver not stepping on the gas. It also maintains a constant speed. The idling actuator is also referred to as "idle speed control". It is controlled by the control unit.
Many factors ensure quiet idling
Nothing can disturb a pleasant driving experience as much as rough idling. If the engine speed constantly varies, the entire vehicle is very unreliable. The driver literally feels like the engine will shut off any second or even break down completely. The idle speed controller is designed to save fuel and make vehicle operation in its idle state as pleasant as possible.
Before vehicles implemented an electronically controlled fuel air mixture intake, the gas and idle speed were controlled by the carburetor. With the help of a variety of valves, nozzles and butterfly valves, this purely mechanical device was able to deliver the right amount of gas in any driving situation. That was also true for idling. In the wake of tighter emission control regulations, mechanical gas preparation could no longer deliver the desired performance and was replaced by the control unit and the fuel injection pump. The elimination of the carburetor has necessitated the development of the idle speed control. It is controlled by the control unit, without the need for the driver to intervene. The parameters needed for a smooth idling are: Air mass, pressing of the gas pedal, outside temperature, engine temperature and engine speed.
Idle speed control operating principle
The idle speed control is technically a bypass valve. The component is installed in a channel that bypasses the throttle valve. It consists of a rotary valve, which is very similar to the throttle valve from a technical point of view. However, its cross section is much smaller at approx. 1/10 of the size. A small stepper motor that is directly connected to the control unit is located directly at the rotary valve. It allows the engine control to adjust the air supply to the cylinder head very accurately.
Idle speed control defects
The idle speed control is located in the air flow, which supplies the engine with oxygen. It sits behind the mass air flow sensor and the throttle valve. However, the wastegate connection is upstream of it. This is activated when the EGR valve triggers. This way, exhausts are constantly led back into the fresh air stream to achieve a reduction of nitrogen oxides. These exhausts can also be contaminated by oil from the engine exhaust. These impurities from unburned fuel and oil residues can settle on the throttle valve as well as the idle speed control. In practice, the idle speed control collects residues significantly faster than the throttle valve. A missing or defective air filter is particularly fatal for the idle speed control. As long as the adhering particles can be removed again, the controller can be repaired by simply cleaning it. However, if the rotary valve's guide is scored or scratched, its function is permanently impaired. Furthermore, the rotary valve can also jam completely. This situation may result in overheating of the actuator, which will cause it to blow in the worst case.
Idle speed control repair
The control unit will generally determine if the idle speed control malfunctions. Other symptoms are: Rough idling or the engine shutting off when the car is stationary.
Idling actuators are quite small and easily replaceable components. Technically, it is not possible to repair these components. One may attempt to use brake cleaner (alternatively: special throttle valve cleaner) to get rid of deposits. An ultrasonic device can also be helpful for this. If this is to be employed, a special cleaning fluid must be used, which does not cause oxidation in the electric motor. Isopropyl alcohol or flux remover are suitable agents for an ultrasonic cleansing. However, the idle speed control must be thoroughly dried prior to installation. A hair-dryer may be used for this.
As with all electronic components, the idle speed control's contact surfaces may be dirty or coated with an insulating oxide layer. Here, thorough spraying with brake cleaner and brushing them off is sufficient to restore functionality. High-quality idle actuators by brand manufacturers The idle speed control is quickly replaced. However, for operational safety reasons, one should always opt for an original or high-quality brand product. ATEC is a good example of a well-established manufacturer of idling actuators. New idling actuators by this popular brand are available for as low as 25 euro.