What is the normal idle speed for a car?
2 Answers
When the engine is warm, the idle speed is generally between 550-800 RPM; when the engine is cold, the idle speed is usually between 950-1300 RPM. Below are detailed explanations about car idle speed: 1. Car engine idle speed is one of the engine operating conditions. The idle performance of the engine has a significant impact on emissions, fuel consumption, and comfort. The engine speed during idle is called the idle speed, which should not be too high or too low. If it's too high, it will increase fuel consumption; if it's too low, it will cause unstable engine idle speed. 2. The idle speed of a car differs between cold and warm engine states. Generally, for a well-performing engine under warm conditions, the idle speed is between 550-800 RPM. 3. In a cold state, the car needs to allow the engine to quickly enter the normal working environment after starting. Therefore, during a cold start, the engine's computer automatically injects more fuel, burning more fuel than normal idle to rapidly increase the engine's water temperature and quickly bring the engine to a suitable temperature. Hence, the engine idle speed is higher when cold, generally between 950-1300 RPM. Once the engine temperature rises to a certain level, the idle speed will decrease to the normal value. 4. Idle speed is not necessarily better if it's lower or higher. Since the engine often needs to operate in idle conditions, statistics show that about 30% of urban vehicle fuel consumption occurs during idle. Therefore, reducing fuel consumption during idle is crucial, which is also a requirement for idle control. 5. The main measure to reduce idle fuel consumption is to lower the idle speed. Foreign research indicates that reducing the idle speed by 100 RPM is equivalent to gaining an extra mile per gallon of gasoline. This requires that during engine idle conditions, the speed should not deviate too much from the optimal idle speed when subjected to external disturbances.
I've been driving for almost twenty years, and idling mainly depends on the engine condition. Right after a cold start, the RPM tends to run higher, possibly surging above 1,000 RPM. Once the engine warms up, it usually stabilizes between 700 to 900 RPM. However, there's quite a variation among different car models. My old Japanese car consistently idles around 800 RPM, while my German car enthusiast friend's vehicle often shows 750 RPM after warming up. If you notice the needle fluctuating up and down or consistently staying below 600 RPM with the engine shaking violently, it's likely due to carbon buildup in the throttle body or worn-out spark plugs needing replacement. Last time my car had unstable idling, cleaning the throttle body cost me just over 200 yuan and fixed the issue.
