Does anyone have a clue what could cause this? I have a 2005 w/ 40K. It has run fine until this past weekend. When I starting I noticed that it didnt start on the turn of the key as normal. It took three times with me giving it gas and when it did finally crank a cloud of white smoke poured from the exhaust? After I get it running it runs fine and cranks up fine after that? Does anyone have any suggestions or similar issues?

Also, I have heard a loud noise like a rock hit my undercarraige. I look to see what it is and I see nothing. I dont think I am really hitting anything...any advise?

Thanks for your help.