What is the idle air flow rate of a car engine?
2 Answers
Under normal conditions, the air flow signal data of a car engine at idle is about 2.5g per second; if it is less than 2.0g per second, it indicates an air leak in the intake system, and if it exceeds 4.0g per second, it suggests that the engine has an additional load. The normal air flow value varies for each engine model, with larger displacement engines having higher air flow values. Faults in the air flow sensor can be divided into two main categories: one is when the signal exceeds the specified range, indicating that the air flow sensor has failed. Modern electronically controlled vehicles have a fail-safe function. When a sensor signal fails, the electronic control unit (ECU) will substitute it with a fixed value or use signals from other sensors to replace the faulty sensor's signal.
I've been driving for over twenty years and have encountered many idle speed issues. Idle air flow actually refers to the amount of air intake when the engine is running at low speed, usually measured in grams per second. There's no fixed standard value—it depends on factors like engine size and temperature. For ordinary cars, it generally fluctuates between 5 to 15 grams per second, lower during cold starts and higher after the engine warms up. If the flow is too high or too low, the car may shake, fuel consumption may increase, or even emissions may exceed standards. For example, my old car had an idle flow around 8 grams, while the new one is close to 10 grams. But if the sensor gets carbon buildup, the flow jumps erratically, and you’ll have to take it to the shop for cleaning. Remember, don’t obsess over the numbers—regularly change the air filter, and focus on smooth driving. If you notice any issues, get them checked promptly—it saves both hassle and money. After all, when idle speed is unstable, safety becomes a concern, especially in rainy conditions when warning lights come on—stay alert.
