I'm on 10yrs/176k miles. Oddly, my startup noise has calmed down significantly. I'm beginning to wonder what kind of noise the chain tensioner might make when it is a little slack on startup. Maybe you know, Gio?The thing is we don't know how long it will go till failure happens. I drove mine for 2 years with the noise.
My problem...From an experience I had two days after buying the Celica, I'd say a chain tensioner with slack would cause a tapping noise that's more plasticky, like extremely noisy injectors. The tensioner applies pressure on a rubberized pad behind the chain guide if I recall correctly. The guide itself is some sort of polymer inserted into an aluminum bracket so any slapping noise will tend to be absorbed by those materials.
This was the case with my GTS. Lift bolt is broken but replacing the OCV Filter allowed me to hit Lift and P1693 is gone.As part of regular maintenance clean these components every 30K or so, both OCV housing and strainer. There have been countless cases of people with lift not working because the strainer was clogged enough to hinder flow of oil to the rocker shafts.
^^ Should see a change EVERY time its engaged. So, I'd guess that there is an OCV, oil pressure, or mis-aligned cam shafts issue.I have also jumped the lift OCV while the engine was running at normal operating temperature and I got a little hesitation from engine the first time, but did it three more times with no change to the idle once so ever!