There is a knocking sound especially when acclerating above 40 mph. It sounds like valve chatter but I'm convinced that is not it. You can hear it above the radio. The sound seems to be coming from in behind the console near the passengers side. I have taken it to the dealership 4 times and it never makes the noise when I take it and they have no idea what it might be. Just curious if anyone else has had a similiar problem. Thanks.