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Question: catalytic converter and O2 sensors...

C

conbon

CEG'er
Joined
Feb 23, 2008
Messages
271
Location
St. Louis, MO
My check engine light has been on for over a year. It started intermitently and then just started staying on all the time. Along with this came the usual poor idle, terrible mileage, etc, etc. Right away I knew it was my O2 sensor, I was just too lazy to replace it. Lately I've noticed that my car has started to smell like rotten eggs after its been running, so now I know the cat is bad too. I want to go ahead and jsut replace the upstream O2 sensor, the downstream O2 sensor, and the catalytic converter. Here's my questions:

1) Where have you guys found O2 sensors for the cheapest price? I know I checked with Autozone a while back and I think they were over $100 for just one sensor, but I found them on Ebay for like $70. Any other places that have them cheap?

2) Is the upstream O2 sensor different from the downstream O2 sensor, or are they the same part/part number? Anybody know the part number(s) off hand, my Haynes manual isn't helping me out on this one....

3) Where do I find a new catalytic converter? I haven't looked into this one, I have no idea where to start.

Any help would be much appreciated. I really want to get my car running smoothly.

-Connor
 
1) Where have you guys found O2 sensors for the cheapest price? I know I checked with Autozone a while back and I think they were over $100 for just one sensor, but I found them on Ebay for like $70. Any other places that have them cheap?

Last time I bought a cheap O2 sensor, it crapped out on me in less than a year. I got a slow response code. :nonono: Spend the money and get a Bosch upper O2

2) Is the upstream O2 sensor different from the downstream O2 sensor, or are they the same part/part number? Anybody know the part number(s) off hand, my Haynes manual isn't helping me out on this one....

Yes, they are different. Read answer #3 for downstream details.

3) Where do I find a new catalytic converter? I haven't looked into this one, I have no idea where to start.

Don't bother. Really, don't. Gut your cat and install a MIL eliminator on the lower O2 sensor. Because you're installing a MIL, there's no need to replace the lower O2 unless you already have a circuit failure code. It's relatively easy to remove the exhaust. Remove the manifold heat shield (this makes it WAY easier to replace the upper O2 anyways), and the bolts holding in the cat are right there. Just need some long extensions to unbolt it. I bet your exhaust hanger in front of the flex pipe is already broken, and your cat strap is broken, so all you have left are some rubber hangers. No biggie. If you still have the resonator and muffler, you won't really notice much of a volume increase in your exhaust either.
 
Ya, those prices were for a Bosch sensor, which is what I'm planning on getting.

I've considered gutting the cat and putting a MIL in. Where can you get the MIL eliminators from? I thought I remembered seeing them on zxtuner but now I can't find them. Or if anyone has the instructions for making your own I got a radio Shack 30 seconds from my house and I'm pretty good with a soldering iron.

Haha, ya...all that stuff is already broken off my exhaust so it shuld be easy to take off. If I had a seond vehicle I'd take it up to school with me and weld a straight pipe through the cat to keep turbulence down, but sadly this is my one and only car so this has to be a one day project.

-Connor
 
There is a website that you can get the proper Bosche sensor for under $50. I'll have to look it up later as I'm not at my computer at the moment.
 
a bosch sensor should run about $50~60 at your local chain parts store ... not sure why you would bother purchasing online and having to pay shipping ...
 
If you are near a Pep Boys, they carry the Bosch O2 sensors in stock for the Contour. I replaced both of mine about 2 weeks ago. Be prepared to spend about $110 average for the pair.
 
Why does everyone think that because you now smell the rotten egg smell the cat is dead?? That is proof it is WORKING. Smell is from F/A ratio going off even more (richer) because too lazy to change it.
 
i think cars that are not driven hard are smell worse when you get on them.

and more often then not your not going to smell the exhaust of your own car when you are driving. its most likely the car in front of you.
 
amc49 said:
Why does everyone think that because you now smell the rotten egg smell the cat is dead?? That is proof it is WORKING. Smell is from F/A ratio going off even more (richer) because too lazy to change it.
Click to expand...
I don't. I've posted a link to an Audi of America article several times... but the site has lost so much useful information lately, you'll have to search the web for it.

ROTTEN EGG SMELL FROM CATALYTIC CONVERTER


The sulphur smell from the exhaust, is actually caused by running the engine/cat convertor slightly lean for long periods and then running under a rich condition (ie going up a hill under heavy load) This is when the sulphur smell (rotten egg) is produced.


Under relatively lean conditions, the sulphur found in gasoline is converted to sulphur trioxide, then during the rich running condition the sulfur trioxide is converted into hydrogen sulphide (rotten egg smell) within the catalytic converter.


Audi of America issued a service bulletin Group 24, #92-04 which detailed this problem. They list the cause as : the gasoline sulphur content and the characteristic of catalytic convertor to store sulphur compounds and release them during rich engine running conditions.


Switching gasoline brands may help. The Oxygen sensor may also need to be replaced to correct a fuel injection

there you go

i also found a thread where a guys' alternator was overcharging his battery.. causing the battery to 'gas off '. Maybe you could look for signs of acid leakage just in case it is this ..
...G.
 
Exactly, gets worse at full throttle because open loop and richer for full power. If converter dead, would be less smell not more.
 
if your convertor was dead then there would be no conversion of anything because there's no platinum to be the catalyst ...G.
 
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