zafarmoh

I purchased a used 2006 Nissan 350z (170k miles) about 3 months ago with very basic mods.
MODS:
K&N Cold Air Intake
Dual Exhaust Setup (without Mufflers at the time of purchase)
Detail on the exhaust setup:
No Cat delete. There is no wye pipe after the exhaust manifold. So there are two separate pipes running from the Exhaust manifold through Cats through the muffler.

About a month ago, I decided to quiet down the exhaust by having mufflers added to each exhaust pipe at a local shop. After that, I started smelling a burning smell while idling at red lights. The engine also threw a code (P2A03 - O2 Sensor Circuit Range / Bank2Sensor1). I took it into a local shop and he cleared out the code and told me to drive around until the code comes back. The code didn't come back for another 2 weeks. After it came back I reset it and took a log.

Does a bad o2 sensor cause burning smell in the engine cabin? or do you think its an exhaust leak from when I had the mufflers installed (the mechanic swears since the mufflers were welded at the end of the pipe, he didn't cause a leak).

Thank you guys so much in advance.

zakmartin

Stick a carbon monoxide alarm in the car and let it sit on idle in a parking lot with the vents turned to recirculate and the windows rolled up. Wait about 15 minutes outside while dribbling a basketball. If you open the door and the carbon monoxide alarm is going off, then you have an exhaust leak entering the cabin.

As for the smell, it could be that the tailpipes don't clear the back of the bumper and are piping exhaust under the bumper and through the rear atmospheric equalization flap. It's also possible (however unlikely) that the new muffler is burning off a protective coating. Any mom and pop shop with a smoke machine or a sniffer can tell you if it's an exhaust leak in less than 10 minutes.

Regardless, as long as that smell persists, I recommend you drive around with the windows rolled down a bit so you don't pass out if the gas is noxious.

EDIT:
Looking at the graphs, bank 1 sensor 1 is reading a tad low. You didn't mention in your post if you deleted the cats when you installed your "Dual Exhaust Setup," which looking at it more closely, you go into no detail over whatsoever. Hint: please go into detail over this entire dual exhaust setup and how it's configured, from the headers to be rear.

zafarmoh

I'll definitely try out the Carbon Monoxide monitor. Added more detail about the exhaust setup
"No Cat delete. There is no wye pipe after the exhaust manifold. So there are two separate pipes running from the Exhaust manifold through Cats through the muffler."

zakmartin

OK. So you have a 2 pipe cat-back setup. Is it correct to assume the O2 sensors are OEM and you're not using a bypass signal?

Looking at your bank 2 fuel trims between 3 and 6 minutes (I'll assume you're in closed loop at this point) I see a couple strange peaks in the stoichiometry, showing a lean condition where the computer's dumping fuel into the system. That could account for a fuel smell coming out of the exhaust and could indicate a vacuum leak or a stuck open injector. It doesn't seem to be an issue between 6 and 10 minutes though, so I'm leaning more toward an intermittent injector issue. At 170K miles on the car, that wouldn't surprise me in the slightest.

zafarmoh

I'm still on the OEM sensors. Not on a bypass signal. I read somewhere that o2 sensor values should be between 0.2V and 0.9V. I was thinking since Bank 2 Sensor 1 value keeps spiking up to 1.2V, might be a faulty Sensor?

zakmartin

You could pull the sensor and have a look at it. If it looks like a sooty mess, and you have no other way to further test it (i.e., propane torch and a volt meter) then go ahead and replace it. Again, with 170K miles on the car, there's the potential that a lot of things will need replacement (if you aren't aware of the care's prior service history.)