Why does an automatic transmission car restart after releasing the brake?

[EmeryDella]

When an automatic transmission car stalls upon braking and restarts automatically upon releasing the brake, this is not a vehicle malfunction but rather the operation of the auto start-stop system. For manual transmission cars, when parking, shifting to neutral, engaging the handbrake, and releasing the clutch will automatically shut down the engine after completing these three operations.

[Arthur]

This situation usually occurs in automatic transmission vehicles because your car is equipped with an automatic start-stop system. When you press the brake and the car comes to a complete stop, the engine automatically shuts off to save fuel. When you release the brake, the system detects your intention to move and restarts the engine to ensure a smooth start. This is a normal function designed to reduce fuel consumption and emissions, especially useful when waiting at traffic lights. Many newer models feature this design, but it operates under specific conditions—such as stable cabin temperature, moderate air conditioning demand, or sufficient battery charge. If the system repeatedly starts or fails, it may be due to an aging battery, faulty sensors, or extreme temperature conditions. It's advisable to develop a habit of regularly checking the battery to avoid issues that could affect driving smoothness. I've driven several automatic cars and found the initial start-stop behavior surprising, but once familiar with it, it feels quite beneficial, even saving some fuel costs in the long run.

[VonColeman]

When driving an automatic transmission car, I also noticed that the engine would shut off after pressing the brake and restart when releasing the brake. At first, I was a bit surprised and thought the car was broken. Later, I realized it was the normal start-stop function in action, designed to reduce fuel consumption during engine idling, especially effective in urban areas with frequent stops and starts due to traffic congestion. The system uses sensors to determine if you're about to drive, preparing to move when you release the brake. This isn't a malfunction, but sometimes it may not work, such as when the air conditioning is set too high or the battery is low on charge. As an ordinary driver, I suggest checking if there's an option to turn it off in the vehicle settings, usually with a button near the dashboard. If the start-stop function frequently behaves abnormally, it's best to have the battery checked at a service center, as small issues can accumulate and affect the driving experience. New drivers might find it a bit unsettling at first, but with more driving experience, they'll get used to it and feel more at ease.

[DiGriffin]

When you release the brake pedal and the car starts again, it's actually the auto start-stop system in operation. This feature is energy-saving and environmentally friendly. Simply put, the engine automatically shuts off when the vehicle stops, reducing unnecessary fuel consumption; it restarts when you release the brake to facilitate moving off, helping to lower emissions. I can feel its benefits every time I drive, especially in urban traffic where it helps reduce air pollution. As long as the system is functioning properly, there's no need to worry—it can extend your car's lifespan and save you some costs.