I'm inclined to agree with the other posters here that social media COULD be an avenue to explore. That said- are you in an urban market, or somewhere a bit more rural? The auto industry can encompass a great many things- are you creating and selling new parts, or are you offering a detailing service, or anything on the very wide spectrum in between?
My point is that there are likely quite a few avenues that will be much more productive than email and cold calling. Check for local trade events (Google is a good resource for that). For less money than you're probably spending on emails, you might be able to get a table and display board at a nearby exhibition. A weekend of face-to-face time with decision makers goes a long way. You could have opportunity to get in front of some local media (the news loves 'soft' stories about new businesses in the neighborhood). You might even be able to offer a sample, similar to a portfolio or proof of concept. The key is to find a way to differentiate yourself. You don't need their attention for long, but you do need to get their attention.

Give me a call- I'd love to discuss this with you in more detail.