I've been getting this weird rattling in my engine bay every since I switched back to the stock header. I'm not sure if that's what is causing it, but it happens around 3-4k. I have a video clip for you all ... hopefully you guys can help me out. Thanks!

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Sound to me like valvetrain is lose. I don't see what changing a header has to do with that sound. Are you sure everything is tight outside the engine?

 

problem with the valves

 

Sorry to tell you, but its the dreaded autotensioner. Every 5th gen has this problem. Welcome to the club.

100% guaranteed. How do I know? I just dropped a boatload of cash to have MINE fixed. It make the exact same noise. at around 1600rpm to 1000 rpm. Above that it is fine and at idle it is fine.

The autotensioner isnt doing its job (IT BE BROKE!) and what you hear is the timing belt rubbing up against the timing belt cover.

Its about $600 with parts and labor through the dealer.

Good Luck.


(Im not sure where you get the "3-4000k" rpm range.)

 

yea im with bones on this one that is definitely not a metallic sound, definitely the T-Belt flappin.

~kris