Hello,

Ok so my 2003 alero (v6) started to sputter recently after changing the tranny oil, and a major tuneup the car feels great however it still sputters, so Ive have been told its the Catalytic Converter.

I was quoted 550 plus tax but, I said 4get it, went home on ebay, and found 1 as cheap 80 dollars. My question is 1st how many o2 sensors are there, and are they actually on the Catalytic Converter or before and after it? I went underneath my car but its kinda hard to tell, I seen 1 02 sensor b4 the cat, and thats it.

Im looking at this one here: http://cgi.ebay.com/ebaymotors/Catco...#ht_1902wt_897

 

Before you blow $550, I would get a back pressure test. Any decent exhaust shop can do it, and it would tell you for sure if your cat is plugged or not.
In my experience GM cars do not play well with aftermarket cats, but I have not tried one on an Alero specifically, so...
What was done on the tuneup?
Usually a plugged cat will throw a code. Also, it will cause the car to run fine at low RPM, but poorly with little power at high RPM.

 

Also on any car that is OBD II (yours is) there will be at least 2 O2 sensors depending on if it's an in-line or a V, H or W block.
So Being that you have a V6 you will have at least 3. One on each side before the converter and one after the converter. If there are 2 converters on the car then you will have 4 sensors.

 

A back pressure test was done, it was confirmed the cat was the problem, now I took the car home because im not paying 550.

I can just see 1 cat, and 1 o2 sensor before the cat, im gonna have to get a better look at it.

Im going to order a car off ebay, ive heard alero dont really respond well to aftermarket cats, but what choice do I have? The link I posted above of the cat, is that 1 good? any suggestions?

 

Is the check engine light on? If so get the code scanned. It will tell you which sensor is bad. Bank 1 sensor 1, bank 1 sensor 2, bank 2 sensor 1.

 

No, no engine light came on.

 

Well then you're kinda guessing. You're going to need to get a good quality scanner on it. They can dig deeper into the computer than the cheap ones and you can get a closer look as to what the sensors are actually doing. They may still be in spec, but close to one end or the other of the "tolerance" and thus causing an issue without throwing a code.

 

The Alero 3.4 has just 1 cat and 2 O2 sensors, one before and one after the cat. The one after the cat is only used to determine cat function, it has nothing to do with engine management. The one before the cat controls the fuel mixture through the PCM.

If you want to change it, Autozone will let you borrow the special socket that is needed. The sensor itself is about $80 USD, and the job takes about 15 minutes.

Since you have had a back pressure test, it seems like the cat itself is bad, so I would go ahead and change it. Personally, I'd do the O2 sensor first, however, just in case it is bad as well. A bad O2 sensor can cause damage to a cat over time.

Sorry, I have no experience with the cat you posted. If they will guarantee it will not throw a code, I guess it would work.

 

That's odd. I was under the impression that all OBD II systems used O2 sensors for each bank of cylinders. I know there are 3 sensors on my 04 s10 and only 1 cat.

 

Hey, ok I found 1 cat locally, it cost me 190 (Candian) Taxes included. It comes with both flanges and gaskets.

It'll b changed tomorrow, ill keep you guys posted..

Im hoping the 02 sensor is good still fingers crossed!