View Full Version : Rotten Egg

07-28-04, 04:55 PM
Can someone tell me what causes the rotten egg smell? I have a 94 STS and I notice that it smells like rotten eggs. :disappoin

I have used the onboard diagnostics to shut off each injector and they all seem to be functioning (RPM changes when each one is shut off).



07-28-04, 05:06 PM
If I'm not mistaken, that happens when your catalytic converter is going bad...

07-28-04, 05:11 PM
That is what I always thought but I also heard that was a myth. So hopefully someone knows for sure.

Thanks for the reply.

07-28-04, 09:15 PM
I believe it is high sulfer fuel. Try a different brand or station. Might also be a rich condition caused by a bad FPR, O2 sensor or leaky injector.

07-29-04, 12:10 AM
It depends on the fuel and the condition of the catalytic converter. If the fuel is too high in sulfur, it can cause the smell. If the cat is bad, it can cause the smell. Like others have said try changing your brand of fuel. Even if it's not a no-name brand, change to something else. Also try some fuel injector cleaner.

07-29-04, 11:01 AM
Sulphur will render a catalytic converter completely useless pretty quickly. High sulphur fuels will, over time, gradually degrade its effectiveness and the rotten egg exhaust smell is typically the sign that the cat is toast. If it's been getting worse over the past few tanks of gas, the cat is probably a goner or close to it. If it just started with a recent fill-up, get that stuff out of your tank. Injector cleaner won't help with this kind of problem. One tank of sulphur-laden fuel, which is highly unlikely but possible, can destroy the cat. Once the sulphur has infiltrated the catalyst media, it is permanently altered and will not be effective again no matter what kind of cleaning you do. It will have to be replaced.

On an OBD-1 vehicle, there is probably no sensor after the cat to determine its efficiency, so you probably won't see any console messages about exhaust system problems. If you got it emissions tested, though, and the cat is bad, it will fail miserably. On an OBD-II vehicle, 96 or newer basically, there should be a sensor after the cat and it would set a DTC indicating reduced catalytic converter performance. It would show up as a SES light, a console message, or both.

Hope that helps... Good luck!

Michael Cowden

07-29-04, 02:29 PM
That is the "Cadillac converter" not the other.....lol

just kidding. I have heard that so often I just laugh, and now I have a Cadillac.