How does Mazda 323 clean the throttle? Sometimes it doesn't come down at idle speed.

It may be because the idle speed control valve or throttle shaft is blocked by carbon deposits, and the engine ECU cannot correctly control the opening of the idle speed control valve when the control circuit is short-circuited, open-circuited or grounded, resulting in poor idle speed. Then it is because of ECU failure or main oxygen sensor circuit failure; The vacuum leakage of intake pipe may cause the engine idle speed to be too high. Remind to mainly check the carbon deposit on the throttle shaft.