I have a stock 00 Max, and I sometimes get a rotten egg smell during hard acceleration and the gas mileage has dropped considerably. The car has 86000 miles, but other than that it seems to run fine. Any idea of what is wrong?

 

I think that means a bad cat.

 

Bad cat converter.

 

Yep, what the previous two posts said. Bad catalytic converter.

 

i get the same smell - and have been told its a bad Cat Converter.
I havent changed mine yet though and the smell only really comes when i am pushin hard on the engine, or in stop and go and stop and go traffic

 

mine smells the same and will keep smelling like that for a long time $$$$$

 

It COULD be a bad cat, or it could just be a high sulphur content in the fuel you use. I noticed the same smell with my Maxima and my Sentra when I push them hard, and it's definitely more smelly when I use gas from my local Texaco station than it is when I use gas from QT, Chevron, or Exxon/Mobil.

*EDIT*

Normally, the stealership will tell me anything to take more of my money, but when I took my Sentra in to ask about the rotten egg smell, they advised me just to switch fuels. The head technician told me that my cat was fine after he examined it, and he also stated that if you run the car hard, it's not abnormal to notice the smell faintly. After I switched fuels, the smell got a little better, but I could still detect it faintly after driving hard.

 

Also, do you run premium fuel like the manual recommends? The Maxima's timing seems to be slightly retarded (set back, not mentally challenged) from the factory, probably because Nissan doesn't want to be responsible for the damage when some dumb-asses fill their Maximas up with regular fuel instead of premium.

If you're using premium fuel, then your timing may not be advanced far enough to burn all of the fuel that it's getting. When you run the car hard at wide open throttle, a lot of that unburned fuel is getting dumped into the catalytic converter. I don't know if you can ever make the smell disappear completely, but getting your timing advanced might help reduce the amount of unburned fuel that gets pushed out of the cylinders (and it could also result in a slight power gain and better fuel economy for you).

 

The cat convertor is made partially from sulfur. Unleaded fuel doesn't contain any sulfur, maybe trace amounts, but what he's smelling is the suflur from the cat, not the fuel.