Weird smell on the freeway...

[johnathan1]

I have noticed this for a while now... whenever I'm on the freeway with the top off, and I get on it, a couple seconds after I let off the gas, I smell this farty-smell...almost like rotten-eggs or something (i know, that's gross)...I was just wondering what that is, I was kinda thinking it was the catalytic converter heating up, (it's relatively new) but is this normal?

 

[3p141592654]

Its H2S forming in the cat. Its especially noticeable when you are running rich because the cat runs hotter and releases any stored sulfur. Here is some more info from wiki....

--------

A three-way catalyst reduces emissions of CO (carbon monoxide), HC (hydrocarbons), and NOx (nitrogen oxides) simultaneously when the oxygen level of the exhaust gas stream is below 1.0%, though performance is best at below 0.5% O2. Unwanted reactions can occur in the three-way catalyst such as the formation of H2S (hydrogen sulfide) and NH3 (ammonia). Formation of each can be limited by modifications to the washcoat/precious metals used. It is, however, difficult to eliminate these side products entirely.

For example, when control of H2S (hydrogen sulfide) emissions are desired, nickel or manganese is added to the washcoat - both substances act to block the adsorption of sulfur by the washcoat. H2S is formed when the washcoat has adsorbed sulfur during a low temperature part of the operating cycle, which is then released during the high temperature part of the cycle and the sulfur combines with HC).

 

[johnathan1]

Okay, so is the smell a bad thing? Does it mean that the cat will need to be replaced again next year?

 

[toml]

Wow, I just came on here to ask the same question... good work guys, I'll address my cat issue by getting rid of it... new exhaust time!

 

[Satan]

It may have just been the cat this time, but if you are consistently having the rotten egg smell, it's more likely your O2 sensor... won't throw a code or anything, but replacing it solved the issue for others (as well as ensured passing emissions).

Do a search for rotten egg...(really)

 

[johnathan1]

o2 is relatively new as well......And the car passed emissions with flying colors. Maybe a cheapy cat? And it only does it when boosting @ around 5-7 psi for a long time on the freeway...

 

[3p141592654]

It is normal to smell it mildly under rich conditions (going up a steep hill on the freeway is where I most often notice it). If it seems especially bad or happens under cruise conditions then check your O2 sensor, and also see if the ECU Vf long-term fuel trim is within limits. You can also try a different brand of gas, as some have lower sulfur content. H2S is toxic above about 300ppm, but you will be nowhere near that limit unless you clamp your lips on the tailpipe! :biglaugh:

 

[toml]

Great info guys. I have a new O2 sensor waiting to go in and i'll look into a new exhaust/cat.

 

[johnathan1]

oh jeez, I just searched and then I remembered that I have a TurboXS RFL vented to atmosphere....

 

[supra90turbo]

bingo, john

 

[theKnifeArtist]

heh, maybe its just the freeway.

 

[toml]

Hehe.

So vented BOV => causing richness => causing the cat to emit H2S = bad smell?

I suppose a little rich running wouldn't cause this but combined with a few things like slightly worn O2 sensor or old cat convertor, could increase the H2S production?

 

[IJ.]

 

[johnathan1]

^^lol...

Ok, so it will eventually kill the cat (lol) if i keep venting to atmosphere, right?

 

[Jaguar_5]

This sounds totally unrelated, but i have a funky smell, sorta like rotten eggs but not quite, it seems to be only if the AC's been running for awhile, when it smells funky i just turn off the compressor, and it goes away... stale R134?

 

[3p141592654]

That sounds like a moldy evaporator. Its a real PITA to get to it to clean it out.

 

[Jaguar_5]

Hmm interesting, i'll look into it
Probably do nothing because it's only if i use AC for a long time, and i'm focusing all my time and money on my turbo supra to get her runnin!

Anyways, sorry for thread-jacking =P

 

[johnathan1]

Ok, so it will eventually kill the cat (lol) if i keep venting to atmosphere, right?

Anyone? Anyone?

 

[Jaguar_5]

Since noones answered yet, i'll give you my complete speculation of what would happen. All cats eventually run out of the catalyst(s), so it would make sense that if venting to atmosphere, causes you to run richer, it would make the Cat work harder and reduce it's life

 

[miggles]

Just be aware that when sour gas (h2s) gets to a higher concentration you no longer smell it *danger danger will robinson* We get some sour gas when drilling oil/gas wells.