Junior (2003)

Two friends on a vacation park behind a seemingly abandoned building in the middle of nowhere to look at their map. They determine they're lost, but can't restart their car.  Since the car is borrowed, they don't want to leave it alone.

So one girl decides to walk back to the creepy gas station they just visited while the other stays with the car.  Never a good idea to split up, especially when you're in the middle of nowhere and you're young females.

When the first girl doesn't come back, the other one flags down a driver who rigs the car so she can follow him back to the garage to look for her friend. Also he can do a quick fix to make sure the car will start.

Eventually the girl ends up in another isolated are, the car dies again, and someone hiding in her trunk starts taping on the car.  At that point I fell into a stupor as there had to have been at least twenty minutes of this girl stranded in her car while it bounces up and down, and she screams and acts afraid.  Just terrible.  And wouldn't you know it's another inbred killer hick movie...  This is why I was able to get this movie as part of an eight movie set for $5.