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