Hi everyone, I have this weird sound in my Xterra 04. At first, I thought it’s lifters. I opened both valve covers and didn’t find anything suspicious.. I even took apart all lifters and examined them. Placed everything back, the sound still present. Now, it doesn’t happen whether the engine is cold or hot. It occurres randomly. To me, it’s sounds more from the bottom than from the top. Here’s the video of the sound. I’ll appreciate all ideas. https://youtu.be/v8GuXpe4qiE

mac,guess rod knock , and maybe just one or two, as if a short lived oil starvation occurred - usually the
"dipsticks" at Lube-Boys forget to put oil back in one outa 30 or so cars , pull out, park'em THEN hear knocking & rush to fill !

I thought so too, thanks. At this moment, the sound became even louder. And it's definitely coming out from the bottom of the engine.