Mazda 323 has low speed and high speed.

Check the vacuum tube for air leakage.

If there is a vacuum leak, the ECM may increase the fuel injection quantity, resulting in excessive idle speed.

If not, please check whether the throttle valve is closed at idle speed. If it is not closed tightly, check whether the throttle valve is stuck due to carbon deposition or locked too tightly. Check whether the air temperature sensor, water temperature sensor and their circuit signals are normal. If the detected temperature is higher than the actual temperature of the engine, fuel injection will increase, resulting in high idle speed.