2001 Pathfinder Engine Rattle Sound

[fixer3]

Early '01 Pathfinder V6 3.5 2wd

Started noticing a rattle sound coming from engine recently, now it's far more noticeable today especially applying heavy gas pedal.
Sounds like tappets/rockers would in low oil - but oil levels are fine.
Only codes are P430 (Cataclean no longer works).

Very hot weather today fwiw, but only light city driving, temp gauge is fine, does it with or without A/C on.

Is this the end?

[VStar650CL]

Give the exhaust pipe south of that bad cat a tap-tap with a deadblow hammer and see if the rattle is coming from there. It's entirely possible the honeycomb in the cat is coming apart.

[fixer3]

Tried hammering both just now with heavy rubber mallet (not dead blow), only the sound of some lite loose particulate at best.
Just took it for a test drive around block, fully warmed up, and no sound at start up or revving at start up, applying heavy gas bursts could only get sound once, it started about 2 seconds after heavy gas and sort of climbed in attenuation until I let off gas but wasn't immediate with gas - though previously today it was when it concerned me.
Weeks before I could only hear a very lite rattle (identical to tappet / rocker? rattle - best I can describe) if I had windows down while driving as it would bounce off walls etc parallel to vehicle to be audible. But if I rolled windows up I couldn't detect it from engine compartment. Today, earlier, it was pronounced, windows up, when applying gas, and I registered it as coming from engine compartment(?). So much so, I drove very slowly home thinking I needed oil. Checked oil 3 times, fill was midway, but I added a half quart anyways before these tests since I was already checking it.
Plugs have not been changed yet (too much going on) ... could it be some kind of pinging?

[VStar650CL]

Ping is very distinct and doesn't sound much like tappets. Maybe a chain guide coming apart or something like that (it won't simply be worn guides, those make a very distinct buzzing noise). If it won't do it in your driveway to be able to use a stethoscope, you might need to rent some chassis ears from the parts store.

[fixer3]

'Chassis ears'... learn something new everyday. Thank you.

I wonder if the Cataclean did something (?) , oh well. Was hoping for a year or two more.
Now I'll have 3 dead vehicles in the drive. lol
(Just wish there were still good new vehicles to buy.)

[VStar650CL]

I learned the value of chassis ears back around '14 from a Nissan DTS. He got sent to us because of an early gen5 Altima that was making the strangest intermittent "thunk" out of the lefthand floorpan. There was no pattern to it, you'd hit the brake or hit a bump and get the noise, then drive for miles and not hear it again. It was loud and you could feel it in your feet. Nothing was the slightest bit loose in the steering or suspension, we had already done a chassis relaxation and even tore the dash out to make sure the factory hadn't left something in or behind the HVAC. We were at wits' end, and the owner was going nuts about it. She was talking lemon law and buyback, so it got serious.

Enter the DTS with a set of chassis ears. After two full hours getting a total of three thunks and relocating the ears twice, it seemed certain the noise was coming directly out of the subframe. Broken weld, we wondered, except it didn't sound metallic. Hmmmm.

"Drop it," the DTS instructed. "Clock your time, I'll see that you get paid." So here I have it lifted and I'm running the left rear bolt out of the frame, and I hear a clatter at my feet. The guy in the next bay lifts an eyebrow. "What was that?"

I look down and between my shoes is an acorn-sized rock. Inspecting the top of the bushing sleeve, there's a visible scrape clear down to the metal. Turns out this woman lived on a gravel drive, and somehow that little rock got trapped between the bushing and the body, completely invisible from underneath the car. Every time it rolled around to the wrong spot and the bushing compressed, the floorpan said ouch. Without the chassis ears telling us definitively where to look, I'm sure we never would have found it.

[fixer3]

I love stories like those. We get focused on the trees & forget the forrest. They're good reminders.
Got called recently to troubleshoot electrical noise in a very large production studio, intermittently audibly buzzing through all speakers / headphones etc. I was the third person they brought in to track it down and they were getting impatient. Traced it to a separately derived system transformer that supplied balanced power (60v/60v) to certain areas of that complex (toroidal transformer). No rhyme or reason but you could hear it buzzz/buzzz...buzzz/buzzz at the transformer then stop with no pattern. Bad core? Bad windings? No noise upstream at the service though. Insulation degradation & arcing on the feeders? Severely hamstrung as to what I could test & isolate, due to every other facility having something going on, I was getting angry as to what they expected me to do so I took a walk to the far side of property to clear my head. There was some painting going on so I thought I would watch while waiting for a text reply from a manufacturer. Then one of the painters picks up a spray gun and their old airless Graco sprayer goes ... buzzz/buzzz.

My sound is on the beat usually, now I'm remembering that these engines have bolts(?) that come loose. That'll be fun if it's just waiting to lodge. I'm actually considering buying one of the new Nissan midsize trucks (dated guts but I feel Japanese is the way to go). Maybe Toyota, but turbo's seem problematic.