How would you know if your cat is bad? Would you be smelling a strong ordor of gas from the exhaust?

yes and you would probably throw a O2 sensor code.

yeah you would definitely get a code. it's a pretty easy thing to remove so just get under there and take it off and look in it. if any of the honeycomb is melted or missing, you should probably get a new one

NO NO NO NO NO NO NO. What is with the bad info being given out? If you don't know what your talking about, then STFU!

You should NOT get a strong smell of gas from a bad converter. If you have a strong smell of gas, its from something else. If you smell sulfer, or what smells like rotten eggs, that is a good indication that your cat is going out. A cat can start to clog and fail, and NOT give a CEL, so just because you don't have a CEL does not mean your cat is fine.

If you have the strong smell of fuel, start by checking all of your fuel lines. Check your fuel filter, look for moist looking dirt collecting around areas where none should be, on the fuel lines or components they connect to. Check out your evap system, a failure may be causing fumes from your fuel tank to vent out under the car.

Tell us what problem your having specifically, and we can help you more. Oh, and ignore any comments from 16yo kids who

yep i was gonna say a stank *** egg smell is always a good tell tale sign of a cat going bad or an already bad cat

^^^ thank you.... some people here dont know their a$$ from their elbow...

besides U NEVER play with cat that has melted that $**** is bad for you...

yea but it would still sometimes throw a O2 sensor code.

it might.. but that rear O2 doesnt do much anyways... but yea it will after a long time of driving with it bad..

so iam not totally wrong on the subject you made it sound like i was 100% wrong.

no i was referring to the post below urs...

If you are not sure about the subject matter, either say you're not sure or don't post.


Thanks.

Folks,....

eventually, what are the symptoms exactly I can know the cat is gone?

you would smell rotten eggs under heavy load

The BEST way to tell if you have a bad cat is to have a tech measure the INLET and OUTLET temp of the cat with the engine running. If the INLET temp is the SAME or LOWER than the OUTLET temp, you have a bad cat. Many techs will just bang on the cat and listen for rattling from the substrate. This won't always work. If the cat is clogged, you'll get power loss.
Things that can cause a clogged cat include: excessive and EXTENDED (KEY WORDS) rich fuel mixture is the usual culprit. So you will want to check teh car out to make sure the engine is running properly.
You won't always get the rotten egg odor.
If you have access to a pyrometer and a lift, then you obviously can check for yourself; otherwise, if you go to shop, INSIST that they check the temps, and WATCH them to make sure they do it.

Thanks guys!!

I think my cat is fine, no codes, no smell of rotten egss, and no smell of gas, was just asking if that would be a symptom.

Anyone else end up with an 02 sensor that was melted and chunks of crap that look like volcanic rock coming out of their cats?

My mechanic, in trying to save me some money, is going to replace the back and center cats, but hollow out the front one because the price he found on it was about $700 ($480 for the center and ~$350 for the rear).

Car has been knocking/pinging under even the slightest acceleration after warmed up. It is now throwing P0430, that's how we were positive I needed at least 1 cat.

Any advice or comments? I read something about needing to make sure those pieces of crap from the cats don't get back into your engine. Any advice on how you make sure of that, and that your engine isn't already screwed? Thanks!

There has to be a reason WHY the cat is bad, and that means you need to see what's wrong with the ENGINE FIRST. Otherwise, you're going to have the same issue again. The car should not ping even under as you call it; "slightest acceleration".
In other words, cat substrate don't typically melt just because.

Back, center, and front referring to...

First, cali or fed spec?

Fed spec cars only have one converter, between the Y and B pipes. Cali specs have two, one on the front manifold and the regular between Y/B.

Assuming you're cali spec (since you mention a front specifically, and who would hollow out the y?), it would be preferable to do a fed-spec conversion on the front manifold, and get an aftermarket y-pipe. That will take care of your front converter and the pre-cat in the Y, for probably the same price (ish) as a brand new Y-pipe (which he would have to get to replace your 'center cat').

P0430 (especially that you mention your O2 being fouled up badly) could easily just be one of the two O2 sensors on the left bank.

Sounbwoy, I understand and agree that I need to find out what's wrong with the engine, but... how do I do that? No codes being thrown...yet.

The cat's replaced (Yes, Cali spec so 4 sensors and 3 cats), but the really bad acceleration pinging/knocking remains.

Mechanic found P0158 and I believe another code and replaced 2 02 sensors. That didn't do it, SES came on again. Then he found a TSB that said replace 2 sensors and then have the ECM reprogrammed. He couldn't do that, so sent me to Nissan. That's when I found out he'd replaced 1 front and 1 rear 02. The TSB said replace the 2 rear. The second rear was the melted one.

Is "left bank" the front? That's the only one not replaced yet... another $175+!

The next thing we're doing is the spark plugs. Hopefully he didn't already order them and will go for colder ones, from everything I've read here.

Sounbwoy, I'm open to other suggestions, please. Thanks.

j/w here... why would a failing or failed cat, smell different than no cat?
cats just cause a chemical reaction...could it be that whatever causes the cat to fail, changes the reaction and produces the egg smell?

Also, if it hasn't thrown a code, chances are it's working well enough to pass emissions, no? Does it take a REALLY bad cat to trigger a CEL?

I was wondering the same thing. Im going to get rid of my cat but I dont want it to smell like rotten eggs.

Actually, I don't have a cat, just a test pipe. It just smells like raw exhaust, you can tell there is no cat. I kinda like the smell actually.
I was just wondering why a bad cat would smell different than my test pipe.

lol I'm so sick of smelling exhaust and gas and burning fluids/coolant.

guess I should fix the leaks first.

im have trouble with my car putting out a rotten egg smell an also cutting out like its cant breath?? Can someone give me some advice on this.... Thanks

Textbook case of a bad catalytic converter. Replace it.

Convertors go bad if they encounter excess fuel, among other reasons.

Other members have ruined their convertors after their fuel injectors started leaking from their pintil caps. A chronic issue our old cars have.

not me, fixed all that ish and have a great running car, well i have a lower intake leak i need to address at some point.