So I had a ticking noise thought to be the TCT. I got mine sand blasted to no avail. Checked all the rocker arms for cracks and checked the valve train. My mechanic even swapped out a tct from his car to put into mine. Didn't work. With everything removed in the valve cover. Im not sure whether or not the TCT is in or not at this point; he suspects it's the timing chain guide. He said it has excessive slack on the tensioner side. Is this something that has happened before?
He thinks either the guide is worn, the bolt holding the guide came loose or the thread got messed up.
This picture is when we did my first rebuild a month ago. Didn't have the noise at that point though. The guide does appear to have a lot of slack.

 

that deep in... maybe change the guides and chain. I wore out the guides on my Xterra and it made a hell of a racket, but that is a common problem. Not sure if the S has the same deal.

 

Definitely planning on changing the chain too since I'm aware it stretches over time.
I hope this solves it.

 

Look closely at the cam chain sprocket on the crankshaft. If you see slot like grooves along the teeth it needs replacing along with the chain. When the chain starts to wear the distance between the links increases a miniscule amount. This make the overall chain longer and also starts to chew and catch on the lower pulley. My psychic diagnosis is the chain catches on the unloaded side of the lower pulley setting up vibrations that make the TCT noise.

Replace the tensioner, guides, chain, lower sprocket, inspect the upper sprocket.

 

How many miles are on your motor? If you do decide to change the chain and guides, I would like to see how much your chain has stretched and how much the guides wore down. Keep us posted...