Where is the knocking coming from? The engine or the transmission? Can you feel the knocking, or just hear it? If you can feel it, is it in the steering wheel or do you feel it in the seat, or the whole car? Is your check engine light on? Let me know, I will try to help. Went through the same problem recently, and even though I have worked on my own cars all my life, it takes a little detective work to find out what is wrong on your own with these newer cars. It could be anything from an unbalanced tire, to valve problems, but there are ways to check and eliminate things. Give me all the info you can, and I will give you the best advice I can. e-mail: [email protected]