Ok when I started my 300Touring today it didnt start all the way so I was like ok I didnt turn the key all the way. So I turned it again and a loud clancking noise came out from under the hood and then it automadicly reved itself to about 2,500rpms. So it freaked me out and I turned it back off and went and looked under the hood. Then I started it again and it did it for awhile and then it stoped. It sounded like it was comeing out from the intake manifold. Drove it around for awhile hasent done it scince. So does anyone have any ideas to what it could be??