The first question that comes to my mind is why you left the lot without obtaining a copy of the contract? Its very hard to tell you what your right are on returning the vehicle when you don't have the contract to look at. However, you likely can return the vehicle if these defects were hidden from you, or if the dealer misrepresented the state of the vehicle to you during the purchase.
Tennessee's Lemon Law does not cover used vehicles. However, there are several other types of laws that can be used to help you in the event you discover that you've bought a used car lemon. First, the Federal Trade Commission
(FTC) has what's called the Used Car Rule that requires dealers to provide consumers with a Buyer's Guide with warranty and other types of information. If the dealer has in any way failed to abide by the FTC Used Car Rule, you may have the basis for a legal claim.
Second, each state has what are called Unfair and Deceptive Acts and Practices (UDAP) laws. If the dealer has, for example, made verbal promises or didn't tell you about issues relating to your used car, you may have a cause of action. Third, Tennessee's version of the Uniform Commercial Code
may provide you with relief. Finally, the Truth in Lending Act and the Federal Odometer Act might also be valuable in obtaining lemon justice.
Thus, you have a right to assert a claim against the dealer for the return of your money and for them to take back the car under the statutes referenced above.
Please let me know if this answers your question.
Zachary D. Norris