96 Sable 3.0L VIN S

Hi Guys,

This is a V6 engine with DOC. It has a very distinctive knock that does'nt sound like a piston, rod or main bearing. It seams like the noise is twice as fast as a piston or rod. Very noticeable at all speeds, even idle. I removed the intake and rear valve cover and didn't see anything out of order. Has anyone ever had a similar experience with this engine?

Thanks Jerry

Louder than a valve I take it? Definitely from the motor? Maybe AC compressor? I have a 97 but so far it's been quiet, 123k miles