Scott Long

My car runs kinda rich, could be the cats hollowing out aren't filtering the exhaust as much, but I think the O2's might need replacing. I don't have cats on my Tbird SC but it doesn't smell like the Audi exhaust, its not running as rich as the Audi.

Also on days when the temp is 60 degrees or below my car will sit there and blow white smoke fumes out the exhaust all day long. 60 degrees or above it will do it until I drive a bit and then it doesn't blow smoke.

Just wondering if this is all O2 sensor related or if I have 2 seperate problems.

thoraudi

The way you describe it I would say one or both of your O2 sensors have had it. I just recently changed one of mine and the exhaust smell is completely gone. I would suggest that you disconnect (on the wires) one at the time and see if the wires are shorted to ground. Replacement is pretty easy. You need 2 shorthandled 22 mm wrench or a 60 mm deep split 22 mm socket. I just bought an aftermarket sensor which works just fine for half the price of original (US$ 80). Unfortynately for you that is in Norway - nice country though.

Scott Long

So I guess one of these days I'm gonna get around to changing my 02 sensors. I just splice the wires into the old ones right? Hopefully they come out easily and I don't break my arm trying to get the O2's loose. There are only 2 on this car?

SquallLine79

From what I recall, 2 per car until 95.5. When my Bentley gets here, I'll be more definite =)

thoraudi

Correct, your car has two sensors. You can just cut the wires from the old ones and reconnect or solder. The sensors should come off easy if you have the right tool. It looks worse than it is.
Regarding O2 sensors; one should definately change them if the cats are changed. With a defect O2 sensor, the mixture will get too rich and you can get unburned fuel ignited in your cats, which in turn will wreck them completely.

Scott Long

If I down shift the exhaust makes a backfiring sound and rumbles (similar to a muscle car) most people think its cool but I'd rather have a smooth exhaust note than a rumbling one. Although I am going to upgrade my exhaust soon I don't like how it pops and backfires on the downshifts. I was told thats the stuff in the cats rattling around and causing that. If I remove the cats then the exhaust will be smooth when I downshift.

So my 93 has 2 O2 sensors for sure? Where are they, above the cats I assume?

thoraudi

The content of your cats has probably spread to the middle and the aft muffler as well. Running some time with defect cats can result in having to change out all mufflers, there is the sound that you say, also there's a chance of plugging the muffler.
The sensors: If you look down into the engine bay beside and a bit aft of the valve cover, you'll notice the exhoust pipe comming out of the manifold on that pipe you'll see the sensor sticking up from the pipe about 10 cm and with 3 leads. You'll need a 22 mm socket or wrench to get it loose.

S6 4RiNGS

and it just bounces around in there... i know i looked at it when i had the exhaust off...

audisrock

There are two unless you have OBDII then you have four of them. Is your OBD connection under the hood or is it located by the gear shifter and E-brake handle? Under the hood for OBDI and next to the gear shifter for II

audisrock

Yeah they're above the cats. Open the hood, and look down along where the exhaust is. You should see a brass or silver colored device sticking out of the top on each side with a few wires coming out of the end. That's them.