Exhaust Smell, Cats gone bad?
Thread Starter
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From: NJ
'08 E550 4Matic
Exhaust Smell, Cats gone bad?
Hey guys,
This has been going on for some time now and Im sick of the smell. After hard acceleration I get this foul odor, Im almost positve that the sulfur content in the gas is ok since Ive refuled countless times since this first started. Ive seached the forums and didnt get a clear answer if replacing them (with some high flow cats
) make the smell go away?
Any help would be great.
Thanks
This has been going on for some time now and Im sick of the smell. After hard acceleration I get this foul odor, Im almost positve that the sulfur content in the gas is ok since Ive refuled countless times since this first started. Ive seached the forums and didnt get a clear answer if replacing them (with some high flow cats
) make the smell go away? Any help would be great.
Thanks
Last edited by C24owner; Oct 13, 2006 at 07:24 PM.
Super Member
Joined: Apr 2005
Posts: 666
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From: Boston, MA USA
03 E320 -wife's car now; 07 Porsche Boxster S - my toy
A quick test of the cats is to find someone with an OBD2 scanner that graphs sensors and look at the before/after (upstream/downstream) O2 sensor voltage swings. If the after/downstream O2 sensor's voltage output looks close to the before/upstream O2 readings, then that cat is running inefficiently. How inefficient is determined by the swing ratio (or switching ratio). Of course, this assumes that the O2 sensors aren't defective.
Just my $0.02 worth.
Regards,
paul....
Just my $0.02 worth.
Regards,
paul....
Thread Starter
MBWorld Fanatic!
Joined: Sep 2005
Posts: 5,769
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From: NJ
'08 E550 4Matic
A quick test of the cats is to find someone with an OBD2 scanner that graphs sensors and look at the before/after (upstream/downstream) O2 sensor voltage swings. If the after/downstream O2 sensor's voltage output looks close to the before/upstream O2 readings, then that cat is running inefficiently. How inefficient is determined by the swing ratio (or switching ratio). Of course, this assumes that the O2 sensors aren't defective.
Just my $0.02 worth.
Regards,
paul....
Just my $0.02 worth.
Regards,
paul....
MBWorld Fanatic!
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From: Philadelphia area
2010 ML550, 2010 E350 4M, 1966 Corvette Convt C2
Perhaps the Cats are worn out and the catalyst is shot. This can be caused by bad fuel or a bad O2 sensor causing it to run rich. Sometimes if you catch it in time and change the O2 sensors if bad you may get the odor to go away but more times than not the cats need to be replaced. Remember CATs are a part that does wear out but usually if all else is correct it will not happen for many miles over 100K.
Super Member
Joined: Apr 2005
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From: Boston, MA USA
03 E320 -wife's car now; 07 Porsche Boxster S - my toy
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From: San Jose area
'19 E63S sedan
BTW, check it soon. A sulfur smell is usually not a sign that the cat is bad, but is overheating. That's usually because the air-fuel ratio is off because of an engine problem. The excess fuel causes the cat to overheat and will do further damage.
I would take it to whoever does your engine work, not a muffler shop.
I would take it to whoever does your engine work, not a muffler shop.
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Thread Starter
MBWorld Fanatic!
Joined: Sep 2005
Posts: 5,769
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From: NJ
'08 E550 4Matic
BTW, check it soon. A sulfur smell is usually not a sign that the cat is bad, but is overheating. That's usually because the air-fuel ratio is off because of an engine problem. The excess fuel causes the cat to overheat and will do further damage.
I would take it to whoever does your engine work, not a muffler shop.
I would take it to whoever does your engine work, not a muffler shop.
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Thread Starter
MBWorld Fanatic!
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From: NJ
'08 E550 4Matic
Just got back from the shop. MAF sensor and o2 sensors are good. Cats are good aswell.
Pre-Cats 240 in and 290 out
Main cats 300 in and 380 out.
Everything checks out good. What now?
Pre-Cats 240 in and 290 out
Main cats 300 in and 380 out.
Everything checks out good. What now?
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Joined: Oct 2006
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Some vehicles may experience sulfur like or rotten egg odor coming from the exhaust. Under certain operation conditions the sulfur may collect in the catalytic converter. When the engine operation parameters change, the sulfur that has collected can be expelled as Hydrogen sulfide (H2S). H2S has a characteristic rotten egg odor. The amount of sulfur in the fuel sold in California is regulated; however the sulfur content sold in other states can be significantly higher. Sulfur content can differ considerably between gasoline brands and location.
A sulfur odor coming from the exhaust does not necessarily indicate there is an issue with the engine running condition. Try following: 1.Change brand of fuel. 2. Change grade of fuel. Note a brand or grade change may take several tanks before a reduction of the condition can be detected.
A sulfur odor coming from the exhaust does not necessarily indicate there is an issue with the engine running condition. Try following: 1.Change brand of fuel. 2. Change grade of fuel. Note a brand or grade change may take several tanks before a reduction of the condition can be detected.
