2012 Quest VQ35DE, sudden power loss, loud exhaust no CEL, only 55k miles, has me stumped, help please

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hellspcangel911
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Car: 2013 Nissan Quest SV

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Hi gang,
We have had this kid hauler since it has 10k miles on it, and for over 4 years, its been well taken care of, bought from a family friend and no issues - it gets pampered with 5k oil changes and 20k CVT services.

My wife was driving it a few days ago, it was raining, she stopped on a slight hill at a red light, when the light changes she accelerated, traction control came on as it usually does and then the car lost power and started to sound "like a honda civic with a can exhaust" (her words).
I went to pick them up, exhaust is intact, no rust, dents, scrapes or leaks, even the flex pipe sections are fine, no CEL or pending codes, we switched cars and I drove it home.
It certainly had less power, especially up hills, and it the left side of the engine sounds like it has a massive exhaust leak, yet there isnt one anywhere.
Before this happened, the car ran fine, i felt a bit of hesitation or slightly rough idle sometimes (so minor i dont think most people would notice) So I planned on doing the sparkplugs.
In the interest of getting the car back on the road I replaced the spark plugs, coil packs, both cam shaft sensors, air filter, cleaned the MAF- and I would say no difference- it might be a little smoother but its hard to tell with the exhaust noise. And still no CEL. All of the original parts looked fine, no surprises.

I ordered a new MAF to try out tomorrow as a few posts have pointed to that, but this has me stumped. The car has never had an issue, never been in an accident and has low (relatively speaking) miles.
If the Cats were plugged would that throw a code?
I never had any noise from the timing chain/guides but if the tensioner let it skip a tooth would that send a code? best way to check timing?

Any help would be greatly appreciated, my family relies on this card for moving our three kids around.

Thank you!
:wavey:


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VStar650CL
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It takes awhile for a dead cat code to show up, and it will only show up if proper conditions for monitoring are met. If one of them is collapsed or plugged, the ECM will never see proper conditions and you may never get a lit MIL unless it's from something derivative. Plugged cats will make the engine howl deeply as the RPM's go up, so it fits your symptoms. If you own a vacuum gauge, the simplest check is engine vacuum. It should read something like 18~20 in/Hg at idle, if it drops way down as you raise the RPM's then the exhaust is plugged someplace. The surest check is to pop the A/F sensors (front O2's) loose one at a time and see if the engine will rev normally when one of them is out, if so the cat on that side is plugged.

hellspcangel911
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Car: 2013 Nissan Quest SV

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thank you for the prompt reply, I'll find my vac gauge and check. Any specific spot to hook it up or just any vac port?

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VStar650CL
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Nothing special, any unported vacuum source will work fine.

hellspcangel911
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Thanks. I’ll try it in the morning. Generally does the car get louder or quieter when the cat is clogged? I’ve had the cat on my Ford explorer cut out in a parking lot and that’s what this first sounded like

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VStar650CL
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I think most people would describe the sound of a clogged exhaust as a moan or howl in a range of maybe 300~500 Hz (a guess), getting much louder as the RPM's increase. It's really a very distinct sound, so if you've heard it before on your Ford and this sounds similar, it's probably the cat.

hellspcangel911
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Sorry I meant the cat on the Ford was cut by a criminal, I came back to the car, started it and it was loud as hell.
This isn’t a drone sound or a loud whining but like there’s a hole in the exhaust

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VStar650CL
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I dunno, maybe one of the upper o-rings on one of your cats gave up the ghost. There isn't much that sounds like an exhaust leak that isn't an actual exhaust leak. If it isn't showing up at idle enough to locate, try having an assistant partially block the pipe with a shop rag. That should make the leak more forceful and easier to locate.

hellspcangel911
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Car: 2013 Nissan Quest SV

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I’m
Getting a solid 20in/hg vac at idle and it jumps up when I rev it but doesn’t drop down. I’m going to bring the car to a friends house and get it on the lift to better inspect the exhaust components bc it’s quiet loud. I stuffed the tail pipe and pegged it at 3k rpm but still wasn’t able to see or feel any leak, two mins later it blew the rag out of the tail pipe.

hellspcangel911
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Holy exhaust leak!
Got the car on the lift and the flange connected to the back of the rear converter had rusted off. The resonator and muffler that are bolted up to the other side were being pressed against the pipe covering it up so you didn’t see it. As you drive, especially up a hill the rear section sways backwards and opens up the exhaust making it louder.
Car drive fine now with with the new ignition components.
I ordered a Y/flex pipe off eBay for $100 and will put that on, I’ll have the original one repaired and ready to swap back for when the eBay one dies.
Hypothetically asking, if that rear converter was replaced with a section of pipe, would they throw any codes?

Thank you for all of your help, so glad it’s not the timing chain!
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VStar650CL
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hellspcangel911 wrote:
Thu May 25, 2023 11:10 am
Hypothetically asking, if that rear converter was replaced with a section of pipe, would they throw any codes?
Not unless it's a Cali vehicle. There's no monitoring of the rear cat on Fed or 49-State vehicles, so it's safe to eliminate. Most guys replace it with a resonator.

hellspcangel911
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That’s great news, thank you.
Thank you again for all of your help and guidance!

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VStar650CL
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:dblthumb:

hellspcangel911
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Just a quick update, the new part arrived and it looked great. I’ve been spraying the nuts on the old
One with Kroil for a few days, all of the hardware came off with the small impact. It was all going good- too good.
The output flange on the new one is too narrow, and the pipe Is about 2” too short. I reached out to the seller but have yet to hear back. It’s a shame bc the part actually looks quite good.
I’m torn whether to try and make an adapter that goes from the narrow flange (bolts are about 4” apart OC), comes out 2” onto the Nissan flange that’s about 6” apart OC.
Seemed like something simple I could
Fab up but I can’t find that Nissan flange.
Option 2, fix the stock one as the flange broke off the pipe but there might be enough wall thickness to mig it back together .
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