The idea that a car can just ... follow people around earns the vehicle a long, suspicious look. Vehicles don't get autopilot, they shouldn't be following anyone around at all, and yet he doesn't get the sense Jack's claiming something impossible. "It damn well better not."

If he's leaving it behind it better STAY left behind! When it utterly fails to move immediately, slowly he turns to follow Jack instead of keeping an eye on it. "And if it tries we'll see how far it gets without tires."