This answer depends on the stage that the transaction has reached. If you have not LOST anything except some of your time (i.e./ they did not CRUSH your vehicle like they did Chevy Chase's station wagon in "Vacation", then you likely have no claim.
Sounds like an overanxious salesman, needing a commission, spoke to soon, but did not have the authority to BIND the company.
Once the Financing Agreement is signed, the deal is completed. As long as you comply with the terms of the Financing Agreement (make timely payments, provide insurance coverage, etc.), the dealership CANNOT take the car back. Even attempting to do so is a violation of the Pennsylvania consumer protection statute, which allows you to sue the dealership for your actual losses and statutory damages. Unfortunately, this is a common practice in the automobile industry and is often referred to as a "yo-yo sale."
The response given is not intended to create, nor does it create an ongoing duty to respond to questions. The response does not form an attorney-client relationship, nor is it intended to be anything other than the educated opinion of the author. It should not be relied upon as legal advice. The response given is based upon the limited facts provided by the person asking the question. To the extent additional or different facts exist, the response might possibly change.