hi i searched and cant find a correct answer for my question.. i recently got a bosch 02 sensor for free from a friend who works at advanced auto.. i no bosch is not recomended but i had no money to buy an acdelco and at my friends store they only has bosch. so i used it because my was that bad.... but now after having the bosch 02 sensor for a week im strating to get a rotten egg smell inside my car.. and from searching on this soite i can not determine which one it is.. im not sure if the catco already went bad from the old 02 sensor or if the bosch o2 is giving me that smell.....?

what do you gearheads think or sugest..?

The failed O2 dumps fuel into the cat and kills it..

so you are saying 100% my cat is bad.?i
i will throw out the bosch o2 sensor and buy a acdelco o2 if i have to buy a new cat....

also now it makes sense that im only getting 12 miles per gallon.. a bad cat would do this correct?
i replaced everything else.

im no expert, but from reading around here, bosch is BAD...only ac delco or denso O2 sensors should be used...and getting 12 miles per gallon, that is probably most definitely a bad O2 sensor...cat should have nothing to do with fuel mileage.....but like i say, im no expert

so i still dont know if your telling me i need to buy a new catco or not?

None of us can tell you that your cat is 100% bad.

You need to replace the O2 and then determine if your cat was murdered in the process. Many times the cat is dead.

OK, so let'* do some diagnostics, shall we?

Do you have a CEL or SES light on? Can your friend at Advance do a scan on your car while it'* running? A decent scanner will easily be able to tell if your O2 sensor is working correctly or not. I would guess...not.

As Bill says above, a bad O2 sensor, left for any length of time as bad, will dump excess fuel into the CAT, destroying the CAT eventually. A bad CAT will usually provide some symptoms for you to check for.

Does your car bog down at higher speeds or after it gets hot? A clogged CAT will have this effect.

Get under your car and use a hunk of wood or rubber mallet to bang on the CAT. What, if anything do you hear?

Now, regarding the very poor mileage you're getting. A bad O2 sensor will certainly hurt your mileage as it will usually allow excess fuel to be dumped in the exhaust, unburned (thus damaging your CAT as mentioned above). A bad catalytic converter will also contribute to bad fuel economy.

So, bottom line is: do a bit of diagnostics first, that way you have an idea of what your problem is before you start buying parts based on our best guesses.

o.k so i will go out later when my wife gets home to watch the kids and ill run some test..

but for now it seems like yous are missing something i said.,..

my old o2 sensor was really burnt up and shot so i put a brand bew bosch o2 sensor in there about 9 days ago because it was free.. so now the next day after putting in the new bosch o2 i started getting that smell.. its not everyday and its not real strong but its there and noticable.... does this change anything besides me needing to trash the bosch and buy a denso.?

No, I think we got it. See, normally that sulfer smell comes from an O2 sensor that is not working correctly. It allows you to run rich, dumping fuel into you CAT. This causes the rotten-egg smell and over time can fry your CAT.

It seems to us that likely the Bosch sensor is not working correctly. Sometimes parts are bad, even when new. That'* why I suggested the testing.

Also, by doing some diagnostics, you may find out if you really need to replace that cat converter or not.

How long did you run it with the original broken sensor? This could have clogged the Cat and now it is trying to clean itself out, thus the smell. Do you have any codes for a rich 02 sensor?