Rotten eggs - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 08-13-2007, 04:07 AM   #1
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Default Rotten eggs

Ok i was driving my car to the mall today and me and my friend were driving like massholes on the way but when i went to WOT my car smelled like rotten eggs on the inside and my friend behind me said he could smell it to, but in me experience that would mean that i need a new cat but any other info would be awesome.
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Old 08-13-2007, 09:41 AM   #2
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Original cat? Mileage?

My '92'* failed at 120k.
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Old 08-13-2007, 09:45 AM   #3
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Generally the rotten eggs smell is from a failing 02 sensor, simple to change and only around 50 bucks at the most (AC DELCO ONLY).
A good way to check for the symptoms is to start the car and simply stand behind the car for a moment, you should be able to smell the rotten eggs smell behind your car coming out of your exhaust pipes. If you had a scan tool you could watch your 02 readings toggle from Rich to lean, they should toggle back and fourth atleast once every half second I seems, as I have found on my car. If it toggles slowly, its time for a new 02.
If It has not been changed recently or within the last 30,000 miles or so, I'd say look into it.
Do a search on "rotten Eggs" or "bad 02 Sensor", might help you further than what I can.
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Old 08-13-2007, 10:15 AM   #4
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As Matt mentioned..typically the O2 fails and dumps a lot of excess fuel. This causes the cat to have trouble keeping up and the rotten egg smell. If your car has been running this way long enough then you probably have a check engine light.

That may or may not indicate that the bad O2 sensor killed your cat.
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Old 08-13-2007, 11:08 AM   #5
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yes its the origianl cat and it has about 135K on it.... when i stand behind my car there is no smell just when im at WOT. but i only did stand bcak there for less then i minute....ill check it again and let it run for a while.
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Old 08-13-2007, 11:13 AM   #6
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Well, it would make sense that at WOT you would get excess fuel that didn't burn off, doesn't it? Therefore, pointing to your O2 as the culprit like said.
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Old 08-13-2007, 12:39 PM   #7
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very true...ill have to pick one up today after work and trow it in andsee what happens..
thanks
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Old 08-13-2007, 02:23 PM   #8
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does any one know what part number i would use for the ac delco o2 sensor is it AFS21 of AFS20 i dont know the difference between them.
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Old 08-14-2007, 07:18 PM   #9
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Default bad catco or 02 sensor? another rotten egg smell

.ujh
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Old 08-14-2007, 08:42 PM   #10
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From what I can make out on the AC Delco site
AFS76 is heated
AFS20 is 3 wire
AFS21 is probably 1 wire.

Which do you have?
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