You can use the "edit post" feature found at the bottom of your original post to add details about the mechanic and your car, or you can use the "reply to thread" feature to add content that way.
Please do not start a second thread. This one can be fixed. Thanks.
To answer the partial question you asked in your thread title now, though: Yes, you can sue the mechanic who has had your vehicle for over a year and still not fixed it. First, anyone can sue anyone else for pretty much any reason at all and, second, it sounds as if the mechanic is holding onto your car for too long and a suit might make sense.
Whether a suit will have merit or not, though, will depend on the additional facts that you provide when you re-post.