Function of air flow meter

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What is the function of a car air flow meter? What are the impacts once damaged? The core function of a car air flow meter is to measure the amount of air drawn into the engine and convert the signal into an electrical signal that is transmitted to the ECU as a key basis for controlling fuel injection, ensuring that the engine obtains the optimal air-fuel ratio mixture under different operating conditions. If it is damaged, the ECU will not be able to accurately obtain intake data, resulting in uncontrolled fuel injection, causing the mixture to be too rich or too lean, ultimately leading to abnormal engine operation, such as decreased power, unstable idle, weak acceleration, and even stalling. The specific function of an air flow meter is to accurately measure the intake volume: the engine requires different concentrations of mixture (air to fuel ratio) at different speeds and loads. The air flow meter monitors the air flow entering the engine in real time through physical or electronic means (such as hot wire, hot film, Karman vortex, etc.), ensuring that the ECU can adjust the fuel injection amount according to the intake air volume. For example, during rapid acceleration, as the intake volume increases, the air flow meter sends a signal to the ECU, which immediately increases the fuel injection volume to meet the power demand. As the core parameter for ECU control of fuel injection, the ECU calculates the optimal fuel injection quantity based on the signal from the air flow meter, combined with data such as engine speed, water temperature, and throttle opening. If the air flow meter fails, the ECU may default to using a fixed value or backup program, resulting in a mismatch between the fuel injection amount and the actual intake amount, which affects combustion efficiency. The impact of damaged air flow meters on the mixture ratio imbalance: excessive fuel injection, insufficient combustion, resulting in engine black smoke, increased fuel consumption, severe carbon deposition, and even damage to the three-way catalyst. Over dilution: Insufficient fuel injection, decreased engine power, idle shaking, weak acceleration, and in severe cases, engine stalling may occur due to misfires. Abnormal engine operation: Unstable idle speed: ECU cannot accurately control the fuel injection amount at idle speed, resulting in speed fluctuations or engine stalling. Weak acceleration: During rapid acceleration, the fuel injection quantity lags behind the increase in intake quantity, resulting in delayed power output. Difficulty in starting: During cold start, the ECU relies on the air flow meter signal to adjust the fuel injection amount. If the signal is incorrect, it may result in extended start time or inability to start. Abnormal transmission shifting: As described in the case, damage to the air flow meter may result in insufficient engine output power, causing the transmission to be unable to shift properly due to insufficient power (such as delayed shifting, impact, or inability to enter high gear), and limiting vehicle speed. Malfunction light on and ECU entering protection mode megabend count: When the ECU detects an abnormal signal from the air flow meter, it will light up the engine malfunction light and may enter a "fail safe mode" (such as limiting engine speed or power) to prevent further damage. Case analysis: Actual impact of damaged air flow meter Fault phenomenon: A 2003 Mercedes Benz diesel engine (M642) experiences speed fluctu

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