I've had this problem ever since I bought the car. It didn't bug me at first but now it's just irritating and I want to get it fixed asap. Fortunately I was able to find videos online about the same problem but I have yet to figure out a fix or what is causing the problem. Here's the videos:

https://www.youtube.com/watch?v=G2egQZ0vG7M

https://www.youtube.com/watch?v=R1sC2Jk-rP4

 

If you mean the sound that happens when coming down from a rev, its the timing chain. Likely a loose/worn tensioner or broken guide. To do a chain on this car you basically need to drop the motor if I'm not mistaken, otherwise its incredibly difficult.

I have the same noise and it runs fine...for now. I have 193K

More info:
http://www.nissanclub.com/forums/200...ing-chain.html
https://maxima.org/forums/4th-genera...placement.html
http://www.ar15.com/archive/topic.ht...=134&t=1159280