Just a heads up. If the 2004 V6 engine is the same as the 2003 take notice. There is a cam chain drive tensioner on the front to power one side. The tensioner for the opposing side is on the back of the engine which means the engine has to come out of the vehicle if the rear tensioner goes bad. I am anal when it comes to maintanence and do not drive in a fashion which anyone would consider abusive. The rear tensioner failed at 70K. I opted to replace the engine with a reman (not rebuilt0 as the labor to pull it out and put it in was the same.
When mine went bad it shouned like a stuck valve or lifter. But is wasn't as the mechanic found where it was coming from with a stetiscope. The replacement part is not expensive, less than a hundred bucks. It's a chicken chit design including thin metal, teflon, and plastic. Sometimes the sound will resemble metal slapping ever slightly on metal. That is the sound the front tensioner makes when the chain is slapping on the cover behind the bottom pully on the front.