Question: Manny replaces the starter motor on the car Ray steals, and it works fine. Once the engine is running it doesn't need the starter motor, so how did all the cars suddenly stop if all the aliens did was fry the starters? Any cars already running wouldn't have been affected. Yes you could argue that it affected their ECU's, but not all cars have ECU's and some still rely on good old mechanical engineering.
Question: Is it realistic to think that Manny, the garage mechanic would have NO idea of what was going on when Ray steals the van from him? After all this is probably about 20 minutes after the Tripod emerged a few blocks away. Surely news would travel faster than that! And you'd think Manny would have felt the massive tripod moving or heard the destruction.