The idle gear control motor, also referred to as the stepper motor, controls the flow of air into the throttle, ensuring that the engine speed does not go below the minimum. It prevents the engine from dying after releasing the accelerator pedal. The motor continually swings the throttle in both directions. One of the most common causes of its failure is carbon. You can tell its failure by problems with starting the engine, the engine dying at idle speed or its uneven operation.
What is the stepper motor?
The idle control valve, frequently referred to as the stepper motor, is located near the throttle of the petrol engine. It doses the amount of air entering the intake manifold while the gas pedal is released. The stepper motor is responsible for the proper starting of the engine, maintaining the right idle speed and stable operation of the engine.
When should the stepper motor be replaced and how is it done?
A faulty stepper motor may cause the engine to stop running after releasing the gas pedal. If the stepper motor is found defective e.g. after connecting it to a diagnostic scanner and reading the error codes stored in its memory, it must be disconnected from the electrical system of the car and its housing unscrewed from the throttle housing to be replaced with a new stepper motor.
What else to keep in mind?
After the replacement the motor requires adjusting by means of a diagnostic scanner. In some car types this process is performed automatically after the car has been driven for a few kilometres with a new stepper motor on. The last stage of the repair consists in using a diagnostic computer again to cancel the errors stored in the computer memory as as result of the malfunction of the faulty component."