The Yo-Yo car sales trap: A dealer calls you back after you've driven the car off the lot and says, "there's something wrong with your financing, we'll need you to come in." Usually thins means they are trying to get a better deal for themselves. Here is a good story on the subject. This actually happened to me back in 1997 at a Ford dealership. However, when I stood my ground and said, "Hey, if you can't get it approved, the car is right here. I'll just go look from something else." They backed down and "miraculously" got it approved.