In Florida, you attain legal capacity at the age of 18. How long has it been since you turned 18? The contract doesn’t automatically get ratified when an infant (legal term for persons under the age of 18;not derogatory) turns 18. There are two ways for a contract to become ratified when you attain capacity, express or implied ratification. An example of implied ratification would be if you kept paying for an apartment for several months after the age of 18. By merely turning 18 and keeping the car for a few weeks, doesn’t automatically ratify the contract. You may still be able to disaffirm the contract if it hasn’t been that long since you attained capacity, especially since you have been having problems with the vehicle. Since you didn’t have (legal) capacity, you wouldn’t be expected to know that you should have gotten a mechanic to inspect the vehicle before purchase. The used car dealership entered into the contract at their own risk. The law allows you to disaffirm a contract within a reasonable time after reaching majority. If you are going to act, I would do it as soon as possible.
Disregard all of the above statements if a significant amount of time has elapsed since you attained capacity