2.7L with 160k miles. A few weeks ago, the engine started to 'knock' a bit when I would start it up. After driving it for a bit, it would stop unless it sat for a while.
My friend and I changed the oil with 5w-30 synthetic. When the oil was draining, the oil color was a brass color and had alot of metal shaving in it. Now after, changing the oil, it has the 'knock' when I start it and sometimes when I drive it for a while. It doesn't do it all the time though.
I haven't noticed any change in performance or gas mileage.
I haven't checked the compression yet., which I think should be the next step.
I'm not sure if knock is the right word to describe the sound but I know it's not the valves either. I have also read about the problems these engines have with a knock but I don't think (and hoping) that's not it.
My friend told me it could be a camshaft bushing.
I've also read online that it could be the main bearings but I don't know.