The contract will be controlling. Was the car sold "as is?" Did you have an opportunity to inspect it beforehand? Did you have the opportunity to have a mechanic inspect it? It sounds like the dealer knew that there were problems with the car in advance. Were the problems that they disclosed consistent with the problems that the car had? I would sit down with an attorney and discuss this matter more thoroughly.
The information provided in this answer does not create an attorney-client relationship. If you are interested in his legal services, feel free to call Chris at (303) 409-7635 at his law office in the Denver Tech Center. All initial consultations are free of charge.