Strange Exhaust Noise - Help with diagnosis please

[Gambit]

Hey all -
So my '88 4WD is making some interesting sounds from the exhaust - and I'm not sure what it is, might be running rich? - I've checked all the things I could think of and replaced a bunch of them - plugs, rotors, wires, coil, checked timing, looked for vacuum leaks, a bunch of sensors, auxiliary air valve etc. Not getting any codes and have kinda run out of ideas.

It otherwise is running pretty well!

Please take a listen here: https://drive.google.com/file/d/1DXN...EitGSYO4j/view

Would love any ideas and thank you!

[PrecisionDriven]

I attempted to listen but have to be granted access to it on Google Drive, so I requested it. Will give it a listen once I get the permission.

[Gambit]

Thanks! I updated it to public... didn't realize nobody could access

[bikeregg]

It's not smoking, does the exhaust have a gasoline or acrid smell to it? If anything, I'd think it might be a bit lean. Idle it for 10 or so minutes, after it cools, pull the spark plugs. That will tell you the fuel/air mixture and what's going on in the combustion cylinder. You can google "read spark plugs" or something like that for reference pictures and what each means.

[JPERL]

sounds like a lean misfire to me more air in the mixture than fuel. Vacuum leaks between the AFM and intake can cause this. Also Since the exhaust and intake ports are on the same side of the engine it is possible that if the intake gasket has a leak it can be pulling in air from outside or from and ajacent exhaust port. If you have emissions testing in your state you likely would see elevated HC in the exhaust.

As a test I would be curious to see if you disconnected your 02 sensor the ECU would default to a rich fuel mixture and in doing so I would listen to the exhaust under full rich condition to see if the exhaust sound improves, less popping, then you could see for certain you have a lean condition

[PrecisionDriven]

Sorry for slow secondary response but have been very busy lately. My best guess is that the catalytic converter is wearing out internally. This article mentions some basic steps you can take to try and diagnose:
https://www.yourmechanic.com/article...-spencer-cates

I tried to find a collection of example sounds on YouTube but no luck.

My theory is that the baffles inside the cat are breaking down, allowing sounds from the engine operation that are normally deadened, to emit in a different sound that is more of a "raw" tone. Once you get it figured out please follow up. Good luck with it.