Need help with exhaust

[dandor268]

Hi.
I could really use some help with an exhaust issue on my 2014 Infiniti Q60s coupe, 55k miles, automatic.

Problem started with smoke only coming out of one tailpipe accompanied by an audible noise at the stock muffler.
I replaced the stock muffler with 2 separate aftermarket mufflers, problem was solved, and smoke exited each muffler 50/50.
One observation that stood out was that inside the stock muffler, it was packed tight with a white cotton like material.  A string of the same cotton-like material led up one of the exhaust tubes towards the engine, I pulled it out not knowing anything about it and closed the chapter on this repair since everything was fine at the time.

2 years later leading into this winter, I noticed smoke only coming out of one muffler.  When I'm in park or at a stop sign/red light, the car gets very bassy and produces a minor vibration.
I thought exhaust leak, but 2 exhaust shops confirmed there was no leak and they could not confirm what the problem is. no rattling noises when they banged on the exhaust and no lights on the dashboard.

Please share some expertise, I'm not sure how to proceed.

[VStar650CL]

That stuff is fiberglass muffler packing used to deaden noise. For it to be coming out like that, the muffler is disintegrating internally. On a conjoined dual like your Q60, when the packing comes out to the front and not the rear, it's also likely that muffler is plugged. There's a venturi effect upstream at the crossover when one side is obstructed, which creates a partial vacuum in the obstructed pipe. Obstructed breathing will also cause an engine to "moan" at higher RPM's and often sound bassier across the board. So it does seem like you have another exhaust issue, although maybe not identical to your first go-round. You can identify a downstream stoppage just by the behavior of the exhaust when you plug each side with a shop rag. If one side blows your hand right off the pipe and the other doesn't, you know that side is blocked.

[dandor268]

That stuff is fiberglass muffler packing used to deaden noise. For it to be coming out like that, the muffler is disintegrating internally. On a conjoined dual like your Q60, when the packing comes out to the front and not the rear, it's also likely that muffler is plugged. There's a venturi effect upstream at the crossover when one side is obstructed, which creates a partial vacuum in the obstructed pipe. Obstructed breathing will also cause an engine to "moan" at higher RPM's and often sound bassier across the board. So it does seem like you have another exhaust issue, although maybe not identical to your first go-round. You can identify a downstream stoppage just by the behavior of the exhaust when you plug each side with a shop rag. If one side blows your hand right off the pipe and the other doesn't, you know that side is blocked.

Thank you for explaining, What would you recommend to troubleshoot the clog? As it's winter i can clearly see smoke coming out the passenger side and barely anything out the drivers side. Do you think the fiberglass could have piled up at one of the Y connections (might explain why there's no rattles)

[VStar650CL]

Yep. There might have been some left in the back pipes after the muffler replacement too, if the clog is on the same side. You can confirm a clog with a shop rag, but the only good way to find the cause is to split and drop the pipes.

[VStar650CL]

PS - If the "smoke" is vapor then you might have water in one muffler and not the other. Do confirm that you actually have a clog and not just a drowned muff.

[dandor268]

Thanks again for the replies. I appreciate it.
Thinking outside the box here, if it is the fiberglass that's causing a blockage, do you think a plumbers snake with that spring tip could reach it and possibly dislodge it? The muffler i bought I recall is almost like a straight pipe (Top Speed Pro Axle back exhaust so i think i could get past the muffler. I suspect the clog is at the midpipe Y, before it connects to the actual Y pipe.

Also, how would I confirm if it was a drowned muffler?

[VStar650CL]

If there's water in there then you'll still have pressure on both sides, just copious steam coming out the side that's waterlogged. If it's a clog, you'll see a large pressure difference.

[DieselGuy]

It sounds like you've already tried some standard exhaust checks, but have you considered that the issue might be related to a clogged catalytic converter? The white cotton-like material you mentioned could be related to this. I would recommend using a diagnostic tool to check for any trouble codes related to the converter. You might find the professional OBD scanners and diagnostic tools at OBDBuy.com helpful for this.

[dandor268]

Thanks for the reply. I have the BlueDriver OBD2 reader and no codes are present for the cats, nor do they rattle or produce a smell.
I tried a couple of ideas since my original post:
1. Shoved a snake up the muffler. On the drivers side it get's stuck at the resonator on the mid-pipe. On the passenger side it goes well beyond the resonator.
2. Temperature check of pipes:
Cats/Y-pipe extremely hot on both sides.
Mid-Pipe leading into drivers-side and passenger side resonators there is a clue. The problematic drivers side is warm while the passenger side is extremely hot. On the drivers side, the clog where it's hot vs cold, appears to be 5" before the resonator and after the Y junction.

The bolts are extremely corroded from winter/salt so dropping the mid-pipe will be challenging. I'm thinking I can cut out and replace the drivers resonator, and look inside the pipe to see if there's an obstruction. If obstructed, I dont' know, try dropping the mid-pipe and shove a crowbar into the Y junction to dislodge whatever is there. Definitely not fiberglass.

Any better ideas?

[dandor268]

That stuff is fiberglass muffler packing used to deaden noise. For it to be coming out like that, the muffler is disintegrating internally. On a conjoined dual like your Q60, when the packing comes out to the front and not the rear, it's also likely that muffler is plugged. There's a venturi effect upstream at the crossover when one side is obstructed, which creates a partial vacuum in the obstructed pipe. Obstructed breathing will also cause an engine to "moan" at higher RPM's and often sound bassier across the board. So it does seem like you have another exhaust issue, although maybe not identical to your first go-round. You can identify a downstream stoppage just by the behavior of the exhaust when you plug each side with a shop rag. If one side blows your hand right off the pipe and the other doesn't, you know that side is blocked.

I FIXED IT!
With the help of a 15foot borescope from amazon, an old plumbers snake and a coat hanger duct taped to the snake with a hook to grab.
Boy were you right with the venturi effect!!
On the working side, I could move the camera from axleback muffler, past resonator, to Y pipe connector. There was some fiberglass here and there in the resonator but nothing of concern, not enough to grab.
On the problematic side, the borescope confirmed the fiberglass obstruction was past the axleback muffler.. in the resonator. A complete wall that was wet and .. clogged.
It took me about 6 hours but I was able to slowly fish out as much as I could, (A crazy amount to my surprise) and then while testing the final result, revving the engine high, it shot out the remaining clogged fiberlgass. It now has that beautiful G37 sound I forgot about, and both side are equally hot.
For picture comparison, I have a size 11 shoe.

[VStar650CL]

Slick. Good work!