Just got this 99 guy told me it needed a fuel pump (it did),started it up,thought the tick tick was the familiar piston slap I've heard on so many 3.1's.But as the engine warmed up the noise didn't go away.I can make the noise stop by disconnecting the plug wire to the center plug on the front(is that #2 or #4?).Is this a rod knock or could the valve train,say a collapsed lifter be causing this?