The Nissan Path

My 03 Nissan Pathfinder emits a strong odor when I start it cold, and it's gotten worse with time. If I roll down the windows or open the door, the fumes get trapped in the cab and it smells toxic (kind of like varnish). I've had two mechanics look at it: Mechanic A said he'd replace everything from the resonators back, but said not to worry about the sensors or the cats. Mechanic B said I need to replace everything from the resonators back and the rear O2 sensors, but he said "the catalytic converters are fine."

I'm puzzled, because it seems neither fix would actually eliminate the smell. Wouldn't it still just come out of the tailpipe? Wouldn't replacing the cats help filter the exhaust emissions? If I had a small child, I would be horrified to let them anywhere near my driveway because the smell is so bad. I want to fix the smell, not just the pipes. I asked Mechanic B what he thought about getting two cats from RockAuto, but he said he wouldn't change them at all. I'm at a loss. What should I do?

A. Replace everything from the resonators back with OEM parts.

B. Replace everything from the resonators back with OEM parts and the rear O2 sensors.

C. Buy an aftermarket exhaust kit like this, O2 sensors and cats from RockAuto, and find a guy willing to assemble it.

D. Sell the vehicle.

Here's a diagram if it helps:

Hi - I dont have an answer, but there are two other resources you could try. The nicoclub website forums and there is an R50 forum on facebook.

If the smell is only there when the car is first started and then goes away then the culprit is likely the cats or actually the fuel itself. The cats don't work properly until they come up to temperature, which takes a few minutes at idle.
The government has been creeping up the ethanol content of gasoline and may have crossed a threshold where it's more noticeable.
Have you tried another source for fuel? you could try a tankfull of non ethanol gas, like what is sold at a marina. It's more expensive but would eliminate much of your exhaust system as the culprit.
The inside of the cats has a screen, much like the mosquito screen on your windows, which glows red hot when up to temperature. Until it gets red hot it's just passing the gas untreated. If the screen is deteriorated then obviously needs to be replaced.

The smell isn't bad once it gets to temperature. However, I've always used non-ethanol 91 gasoline from Casey's, so I don't think ethanol is the issue.

Can I rule out the cats if the smell diminishes after it's warmed up? Could the issue be upstream of the cats? Maybe the smell is just from the leaks in the exhaust. But wouldn't repairing the exhaust just redirect the bad smell out of the tailpipe?

If you suspect that you have exhaust leaks in the headers or exhaust gaskets you should address them. Re-directing the gases out the tailpipe is how the system is supposed to work. Those gases smell bad and are deadly. Some of the R-50 models have problems with the headers cracking. SMJ would probably know more about which models were likely affected. You should be able to hear a decent size leak or find it by looking for the carbon buildup.

Hooligan wrote:If you suspect that you have exhaust leaks in the headers or exhaust gaskets you should address them. Re-directing the gases out the tailpipe is how the system is supposed to work. Those gases smell bad and are deadly. Some of the R-50 models have problems with the headers cracking. SMJ would probably know more about which models were likely affected. You should be able to hear a decent size leak or find it by looking for the carbon buildup.

Those were the early R50 Pathfinders ('96/'97) with the VG33E engine. It was usually the right bank and then they re-designed the manifold and the heat shield.

I didn't think about the headers. But since this is the VQ35DE engine, I'm hopeful that's not the problem. Everything from the resonators back needs to be replaced, though, that I know. One shop quoted me just over a thousand bucks.

Since my original post, I decided to purchase a newer vehicle. The ol' Pathy is sitting on the street with a For Sale sign now. I just couldn't bear the thought of spending that much money on something that should fix the problem, but might only reduce it somewhat. In hindsight, I might have rushed too quickly to get a newer vehicle. I could've replaced the exhaust 20 times over with what I'm about to pay in car payments.