02 maxima has a gunpowder smell after driving hard, or on the highway. I think it is most likely cats, but how would I tell if it is pre cats, or the main cat? Thanks

 

If by gunpowder you mean sulfur/rotten egg then it is definitely the cats. Virtually impossible to tell which as far as I know without it throwing a code or opening it up to look. Either way you might as well punch out the main cat and reinstall or just replace it with a "racing catalytic converter" and then do the ol' nonfoulers or o2 simulator.

 

either that or your battery is bad, which gives off that rotten smell and it overheats, you could check see if you have excessive gassing of the battery

 

For the love of VQs everywhere, delete the cats!

 

I'm about to get this done myself

 

I think I may be experiencing this myself. Just recently. Seems to come from the passenger side. Caught it after backing into the garage. How is the motor running otherwise?

 

The car is running great itself, just waiting for it to throw a code, most likely getting a stainless cat from warpspeed and some headers.

 

Where do you fill up gas? I ask because I've experienced a rotten egg smell in another car when using certain budget gas stations.

 

I get gas at QT, or Murphy, only 93.

 

I know the typical smell for a converter going out - this ain't it. At least in my experience. Kind of why I replied 'cause I had this smell I could not even describe really. When you said "gunpowder" ...

Here's the thing in my case. I've been debating for about 2 weeks now whether I have a rod knock or a pre-cat going bad (sound). Been babying the car not knowing what the hell it is. Then this smell kind of like what you refer to.

Distinctly different though.