I'll start out by saying that i have an AEM intake and custom exhaust. I may be running rich from the evidence in the paragraph, but please read-on.
I'm driving on the freeway and i get a whiff of rotten eggs, i'm freaking out cause that better not be my cat, i mean i only have an 04, also i can see a lot of carbon residue in my muffler and i still have exhaust leaks, I got a cat-back exhaust system custom made from a local midas shop, and i put my hand to the leak and i bring my hand out with black on it, also i can't tell if its just the exhaust system but when i down shift and its rev-ing down it pops, it sound beautiful otherwise but i don't like the popping.
So if anyone has anything that they are able to tell me, that would be wonderful and most appreciated.
~Franz!
"Sink or Swim, Do or Die!"
Rotten egg smell, usually indicates your cat. If you're running rich, your o2 sensor could be shot, possibly from the exhaust install. Either way, you'll need a new cat, and I'd swap the o2 sensor as well.
I may not know much about cars, but I know two things....
1) Breaking things is expensive, and
2) Horsepower isn't cheap.
I have also been told the rotten egg odor is merely caused by the sulfur content in the gas.
I experience it occasionally, not every tank.
As far as the popping noise, I'm not sure what it is, but I hear the same thing with my 2.4 with stock exhaust and a turbo muffler.
I know it's JUST a Cavalier, and I'm sorry if I hurt your ego.
That popping you hear is caused by the honeycomb catalyst in the catalytic converters disintegrating and blocking the exhaust. The "poof" or "pop" sound you are hearing is the exhaust finding a different exit path.
- 2004 Cavalier - 124k, owned since new
Rob S wrote:That popping you hear is caused by the honeycomb catalyst in the catalytic converters disintegrating and blocking the exhaust. The "poof" or "pop" sound you are hearing is the exhaust finding a different exit path.
Ummm, no. That popping is normal for free flowing exhaust. If you had just taken your factory muffler off and changed nothing else, that popping would be there.
More than likely your o2 sensor is shot and needs to be replaced.
O2 sensor?
What does that have to do with a rotten egg smell? Dude.. it's sulfur or his cat, which I doubt it's the cat.
And you already said the noise is due to the exhaust...
So you blamed an ODOR on a sensor?
Sensors pick stuff up man, they don't give off odors.
I know it's JUST a Cavalier, and I'm sorry if I hurt your ego.
z24challenge wrote:O2 sensor?
What does that have to do with a rotten egg smell? Dude.. it's sulfur or his cat, which I doubt it's the cat.
And you already said the noise is due to the exhaust...
So you blamed an ODOR on a sensor?
Sensors pick stuff up man, they don't give off odors.
Yes, but if the O2 sensor sent out to rich of mixture it would wreck the cat.
- 2004 Cavalier - 124k, owned since new
The mixture is dictated by your air intake and fuel system, amongst other things like combustion etc......
The sensor only SENSES the mixture. It doesn't send it.
It reads the mixture to tell your PCU what is going on with the car.
I know it's JUST a Cavalier, and I'm sorry if I hurt your ego.
If it were the o2 sensor, you're check engine light would come on. The check engine light is specifically tied to the emmisions control system, which the o2 sensor regulates. So if that were wonky, you SHOULD have a light.
I agree it sounds like the either sulfur content in the gas or your cat. If it only happens occasionally, then it's probably the gas. If it gets worse, hate to say it, but that is a classic shot-cat symptom.
Alrighty....since there seems to be confusion here on what in the heck everyone is talking about, let's go over it all again.
Symptoms:
- Soot on muffler
- Rotten Egg Smell
- Popping Exhaust
Possible Explanations:
- Soot on Muffler
-- Engine is running rich
- Rotten Egg Smell
-- Engine is running rich
-- Bad gas
-- Bad cat
- Popping Exhaust
-- Exhuast Leak
-- Welcome to the world of free flowing exhaust
Now when the O2 sensor was mentioned it is because it is one of the key points used by the computer to determine the Air/Fuel mixture. If the O2 sensor isn't reading what it is supposed to be reading, it could cause the engine to run rich causing the first two symptoms that were described. As for the argument that the computer should throw a code if the O2 sensor was bad?? Well my friend, you should just go apply at the dealership and be one of the monkey mechanics that can't think on their own. I get that response enough when I take it to the dealership.
Service Manager - "Well the computer isn't throwing a code, so nothing is wrong."
Me - "So your saying that all of the soot on my muffler is normal along with the smell of gas and rotten eggs?"
SM - "Nope, something isn't right."
Me - "So fix it"
SM - "No codes, nothing to fix."
Me - "So there is nothing wrong."
SM - "It is running rich for some reason."
Me - "Thank you captain obvious. Replace my O2 sensor and bill me if it doesn't fix it."
Guess what, bad O2 sensor. 3 times in 6 years my O2 sensor has done exactly what has been described. I fought the dealership each time and won.
Now it is possible that it isn't the O2 sensor that is bad, but from what has been presented so far that is what I would be leaning towards.
You mentioned exhaust leaks? Where are the leaks? Did they weld everything together or clamp it? Or are you assuming leaks becuase of the popping?
You make a good point about those things not always throwing the proper code. That's why I said he SHOULD have a light. I didn't mean to disregard the possibility altogether. I hate dealerships for that same reason, so I definately didn't mean to sound like that's what i was saying.
Is there any way i can tell if my O2 sensor and cat is bad with out a code scanner?
"Sink or Swim, Do or Die!"
A code scanner won't show you anything either. Your CEL isn't on, which means there aren't any codes being thrown. As far as I know, the only way to "test" it really is to have it hooked up to a computer that actually shows the voltages coming out of the sensors. Then as long as the person using it knows what they are looking at, they can pay attention to see if the sensor is actually behaving like it should. It obviously isn't far enough out of whack to trip the CEL, but it probably is sitting right on the limits and therefore causing your engine to run rich.
