Take it in and let us know what Infiniti says. Hopefully you'll have a good experience with your stealership.

Is it throwing any codes?

 

valve lash is the gap between the valve stems and whatever the cam rolls over to actuate them. as i said im not to experienced with the vq series, but from experience with other engines after the engine has had a few miles put on it, the valve lash can change and not be up to spec anymore… sometimes you will hear the ticking when the engine is cold but after it heats up and some parts expand the ticking from the valve lash can disappear. but this will be more of a higher pitched tick then a "knock." but this is just another possibility

 

We have hydraulic valve adjusters.

 

Well it seems the knock is gone now. She said the car was on empty & so stopped to fill up & when she started it back up there was no knocking. I checked it when she got home & it was quiet. Is that normal when low on fuel?

 

there is a tsb for engine knock maybe this maybe not if it comes back check this

 

There was no engine light on.

 

Maybe she got bad gas last fillup or didn't put in hightest?

 

Ahh yes, the old low on fuel knock? Like a little child that's starving crying, "feed me" "feed me" (that's a new one)
Gary