What is the ideal idle speed for an automatic transmission car?
3 Answers
For automatic transmission vehicles, the general idle speed range is between 500 and 850 RPM. When the vehicle speed reaches 20 km/h, you can shift to 2nd gear at 1500-2000 RPM, and when the RPM exceeds 2000, shift to 3rd gear, bringing the vehicle close to 30 km/h. Similarly, shift to 4th gear when the speed reaches 50 km/h. This is because shifting at 2000 RPM can easily cause carbon buildup, so the fuel-efficient RPM range is between 1500-2000 RPM. Car idle speed is the minimum RPM set to ensure the engine doesn't stall and runs smoothly. As long as these two conditions are met, the lower the idle speed, the better. As long as the engine runs smoothly without shaking or stalling, it's acceptable. A lower idle speed saves more fuel because the vehicle is stationary at idle, meaning no fuel is consumed for movement. A higher idle speed has only one drawback: increased fuel consumption. Most cars have an idle speed between 600-850 RPM, with 700-800 RPM being the most common. Different car models have different engine speeds and idle values due to variations in engines. Generally, the idle speed ranges from 500 to 850 RPM, while the idle speed during a cold start can be around 1500 to 2000 RPM. Once the engine coolant temperature returns to 90 degrees, the idle speed stabilizes within the specified range.
After driving automatic transmission cars for so many years, I've found that maintaining an idle speed between 700 and 900 RPM is quite appropriate. If it's too low, say below 600 RPM, the car tends to shake or even stall, and starting feels less smooth. On the other hand, if it's too high, exceeding 1000 RPM, it burns more fuel and increases engine wear. Especially in cold weather, the idle speed might be higher when you first start the car, but it should gradually drop to around 800 RPM. If your car's idle speed is often unstable, fluctuating up and down, it could be due to carbon buildup, a dirty mass airflow sensor, or aging spark plugs. It's best to regularly maintain and clean these components. Remember, a lower idle speed isn't always better; balance is key to protecting your car.
From my experience in car repair, the ideal idle speed for automatic transmissions is usually around 800 RPM, but this varies depending on the vehicle model. Gasoline engines typically idle between 700-900 RPM, while diesel engines may run slightly higher. If the idle speed is too low, it can cause rough idling and insufficient power; if it's too high, it leads to increased fuel consumption and noise. The simplest way to check if the idle speed is normal is to observe the tachometer on the dashboard when parked. Significant deviations may indicate issues like a clogged throttle body or faulty O2 sensor. It's advisable to pay attention to the difference between cold and warm engine states while driving – higher idle speed during cold starts is normal, but it should stabilize around 800 RPM once the engine warms up. Regular air filter replacement and cleaning of the electronic control unit can help maintain stable idle speeds.
