Shuts off when put in gear

Hi and thanks for using 2CarPros.

Unlike a manual transmission that requires you to depress the clutch to stop, an automatic transmission uses a torque converter. Based on your description, it sounds like that is the problem. A torque converter uses transmission fluid to transfer power, and effectively disengaging the engine from the transmission. When you come to a complete stop, the torque converter starts slipping, allowing the engine to keep running. If your vehicle gives you the impression of a manual transmission that doesn't have the clutch depressed, my first suspect is the torque converter.

Let me know if you have other questions.

Joe