Why do I hear a low humming noise from my 2005 Honda Accord after had the air filter replaced The mechanic says that it is small electric motor have part of engine help?

The low humming sound you hear after having your air filter replaced is likely coming from the Intake Air Control Valve (IACV) or the Throttle Position Sensor (TPS). These components are part of your vehicle's engine and help regulate the flow of air and fuel into the engine.

The IACV is responsible for controlling the amount of air that enters the engine when idling. It does this by opening and closing a small valve that bypasses the throttle body. When the IACV is working properly, it makes a quiet humming noise that is barely noticeable. However, if the IACV is dirty or faulty, it can make a louder humming noise.

The TPS is responsible for communicating the position of the throttle plate to the engine control unit (ECU). This information is used to calculate the correct amount of fuel to inject into the engine. When the TPS is working properly, it makes a quiet clicking noise. However, if the TPS is dirty or faulty, it can make a louder humming noise.

If you are concerned about the humming noise coming from your engine, it is best to take your vehicle to a qualified mechanic for diagnosis. They can determine if the noise is coming from the IACV or TPS, and they can perform the necessary repairs to fix the problem.