A google of WordPress car repair themes brings up a few links, but as you say the themes are not that good, I think it might be better to plan the theme a bit more around the content.
Just a good quality or premium WordPress theme will likely fit as well if not better, it will turn into the theme you want as you add the content.
If we think of the content, home page, our services, our location, contact information and customers.
The theme plugins, most of these would be around contact, get a quote, call us, contact us, customer satisfaction (endorsements).
These do not require a custom "Car Theme", look at some other good websites and content, and most of these like in the link will not have a specialist theme, just a nice clean website with easy to navigate information.
HTH
David