14 replies to this topic

[James100]

What is the brand and part # for your O2 sensor .... I have heard the cat getting fried because the O2 sensor was bad and the people never changed them.. They drove around with the Cel light on and ignored the problem......This made the cat overheat and crack up eventually.

Edited by James100, 13 March 2006 - 09:03 AM.

[andrew_the_fox]

Except sometimes I smell rotten-egg frm under the car
a muffler guy said my new cat color has changed and might be overheating.
Anyone has any idea?

Dr. Fox Diagnosis


I aint even a pro like the guys on this forum but those are the tell tale signs: YOUR RUNNING TOO RICH!
First, scan your OBDII for error codes, you might find one indicating that your engine is running too rich which causes the catalytic converter to overheat. Check the fuel pressure regulator, and check for faulty or clogged fuel injectors.

The rotten egg smell that you mentioned is usually also caused by a fuel mixture in the engine that is too rich. The catalytic converter may be faulty but before you replace it the fuel mixture needs to be corrected.

[1997850T5R]

Also I must add, 20,000 miles is fine operationg range for cap and rotor but, I would change the plugs themselves at 10,000 miles at the least. You might want to pull them atleast to see if they have deposits on them which indicate running rich. Buy some champion coppers and throw them in. That should help atleast somewhat.

[1997850T5R]

Thanks for the advice.

If my engine is running rich, which i think it probably is, won't the check engine light go off? I don't have a ODBII reader. If I get one, will it tell me what's wrong?

How do I adjust the fuel mixture? using the ODBII reader? For older Bosch F.I. on my BMW and Alfa, I can adjust it by the screw on the airflow meter. But the volvo airflow meter looks different.

I think I'll change the wires and the plugs this weekend.
RK850

As far as I know there is no way to change the A/F ratio on our cars without the ECU being reflashed. This would require more than an OBDII reader, and is not really your problem anyway. And also, unless extremely rich you would not be getting a CEL code. I would do those two maintenance things as soon as you can, and most likely replace your O2 sensor again. I don't know how you could have ruined a cat in just 6 months, unless you were running VERY rich. Get these things done and your CEL will go away for sure, but I dont know about the rattling your experiencing in the cat. I would just cut it out and put a straight pipe there if I were you...

[James100]

Thanks for the advice.

If my engine is running rich, which i think it probably is, won't the check engine light go off? I don't have a ODBII reader. If I get one, will it tell me what's wrong?

How do I adjust the fuel mixture? using the ODBII reader? For older Bosch F.I. on my BMW and Alfa, I can adjust it by the screw on the airflow meter. But the volvo airflow meter looks different.

I think I'll change the wires and the plugs this weekend.
RK850

You should register and put location in this will help out....

Depending where you live you can go to Autozone for the OBDII reading.....In CA (Los Angeles area) you put a deposit down on it as a loaner tool of about $150....In other places(states) I think they will read it for you for free...So you really dont need to buy one if your CEL light is on if you want to save cash for now....

I dont believe you will have any codes in there because your CEL light never came on so there shouldnt be anything in there to read....So I dont think that is going to do you any good...But I was just reading someones other post today (Tuesday 3/14) and he says when he clears codes he keeps getting 443 (Three way Cat efficiency) and it doesnt throw the check engine light.....So maybe you should try to read codes....

I would check your plugs first to see whats going on in the engine...The O2 sensor affects fuel so I would want to know the part # to make sure it was the correct one....

Edited by James100, 14 March 2006 - 07:02 PM.

[James100]

But I was just reading someones other post today (Tuesday 3/14) and he says when he clears codes he keeps getting 443 (Three Way Cat efficiency) and it doesnt throw the check engine light.....So maybe you should try to read codes....

Here is the post Cat

Edited by James100, 14 March 2006 - 07:05 PM.

[andrew_the_fox]

I don't know how you could have ruined a cat in just 6 months

leaded racing fuel?

[Crabolsky850]

Dont feel bad, your not the only one with this problem. I too replaced my cat 6 months ago, and I now also have another cat problem.

Its not burning or throwing off any smell. I went through everything and everything (at least on surface) is running tip top. I am averaging 23-24 miles per gallon, O2 sensors are new etc etc... but the cat is now falling apart (loose inside).

Its A&B brand, which is one of the nicer more expensive aftermarket cats.

[1997850T5R]

Dont feel bad, your not the only one with this problem. I too replaced my cat 6 months ago, and I now also have another cat problem.

Its not burning or throwing off any smell. I went through everything and everything (at least on surface) is running tip top. I am averaging 23-24 miles per gallon, O2 sensors are new etc etc... but the cat is now falling apart (loose inside).

Its A&B brand, which is one of the nicer more expensive aftermarket cats.

That really sucks... You might want to check your exhaust hangers for excessive wear but... Other than that I have no idea what could be ruining a high dollor cat in 6 months.

[James100]

Some posts point to the actual fuel being put in .........You should read these especially #4........ here are some links
1)1994 850 Catalytic Converter, What's that rotten egg smell?
2)Sulfur/rotten Egg Smell
3)New Cat Now Rotten Egg Smell, new cat rotten egg smell
4)Slight sulfur/rotten egg smell from high flow catalytic converter

5)Below is off an other site
"A harsh smell coming from the exhaust can usually be attributed to the use of fuel that contains methanol (Although in most places it is not supposed to be sold). When using this fuel, a sulfur smell can be emitted from the exhaust which can range from a mild odor to a rotten egg smell. To avoid this smell try changing the place where you purchase fuel! Catalytic Converter failures can also cause this same smell!"

Edited by James100, 15 March 2006 - 06:56 PM.

[RK850]

Well i replaced the spark plugs and this is what the old plug looks like after 40,000 mi. The rest of the plugs look just like this one. Does it look like it's running rich?

I just put my K&N cone filter back in the car. In case if it does run rich, the cone filter can give the engine more air and run a little less rich, I think/hope.

Thanks for all you guys input on this.


RK850