Better to have a 13% rate on $4,000 than $40,000. You can get a credit union car loan for .99-3.99% with decent credit, and 13% is more like a bad-to-decent credit card. If your credit is good enough, you could go to a local credit union and talk with a loan officer about a refinance (the whole public purpose of credit unions, which are nonprofits, is to extend credit to people who have difficulty getting it elsewhere). You'll pay almost $400 in interest alone on the car in the next year. It may not sound like much, but it really is for how low-value the loan is overall.
That said, don't beat yourself up about your past mistakes. Your Money or Your Life, one of the core texts of this movement, emphasizes "No Shame, No Blame" for the past, and to focus on what you can do going forward.