This is a re-post. I was really hoping someone out there has seen this problem, if it even is a problem. I hate to go back to the dealer without any causes and have them screw around with it. Car is a brand new 2010 Civic.
It happens when car has sat over night or all day at work, when I go to start it, as soon as the engine turns there is a knocking/banging sound. Real quick not really loud. Car will start fine. Doesn't happen every time. It has been cold around the 20's outside, car in garage. If I shut it off and restart it sounds fine, no noise. Doesn't seem like anything internal in engine. I was thinking belts, or belt tensioner. Any other ideas?

 

Ya gotta record it with a video or something. Get a really high quality microphone too to supplement the video recording if you can.