1. Hot Wire: A very fine platinum wire is heated electrically to a specific temperature. This wire is positioned within the airflow path.
2. Airflow Cooling: As air flows through the sensor, it cools the heated wire. The amount of cooling is directly proportional to the volume of air passing by.
3. Resistance Change: The platinum wire's electrical resistance changes in response to its temperature. A cooler wire has higher resistance, and a warmer wire has lower resistance.
4. Measurement: The sensor's circuitry continuously monitors the wire's resistance, which is then translated into a voltage signal. This voltage signal represents the amount of airflow. A higher voltage indicates a greater airflow rate.
5. Signal to ECU: This voltage signal is sent to the Engine Control Unit (ECU). The ECU uses this information, along with other sensor inputs (like throttle position, engine temperature, etc.), to calculate the precise amount of fuel to inject for optimal combustion. The goal is to maintain the correct air/fuel mixture for efficient and clean operation.
In short: The 1991 Camry's MAF sensor measures the cooling effect of incoming air on a heated wire. This cooling effect translates to an electrical signal that informs the ECU about the mass airflow, allowing for precise fuel injection. A malfunctioning MAF sensor will often lead to poor engine performance, rough idling, and potentially even a check engine light.
