Rattling Catalitic Converters

[hot37shot]

Hello ppl!

I have a 99 Sierra 2wd with a 5.3l and about 90k mi. I have had a problem with my catalytic converter’s rattling for quite some time(20k mi). It sounds like a penny inside a tin can at idle. The truck runs great with no power loss , no over heating, good mpg, no engine codes and exhaust hangers/pipes are tight. Is it imperative that I replace the cats, because I really do not want to drop $1000. Also, I have a minor misfire at idle and in gear. Could this be related?

Thanks for the insight!

Shawn

[Mark_in_Tulsa]

Yes you need to replace them. By federal law they are warranted for 80K miles, so you waited a hair to long.

 

And a cats only cost 60 bucks if you shop around. Not a 1000.

[hot37shot]

Yes you need to replace them. By federal law they are warranted for 80K miles, so you waited a hair to long.

 

And a cats only cost 60 bucks if you shop around. Not a 1000.

Noo way. I live in California who has the harshest emissions laws. I was told aftermarket cats would not pass smog. So the factory cats are the only way to go. They are sold in pairs and are very expensive. I would love to get some aftermarket cats, cuz I know they will flow better and sound louder. Also, will aftermarket cats throw engine codes and last a long time? Any feedback is great!

Shawn

[Mark_in_Tulsa]

Yes you need to replace them. By federal law they are warranted for 80K miles, so you waited a hair to long.

 

And a cats only cost 60 bucks if you shop around. Not a 1000.

Noo way. I live in California who has the harshest emissions laws. I was told aftermarket cats would not pass smog. So the factory cats are the only way to go. They are sold in pairs and are very expensive. I would love to get some aftermarket cats, cuz I know they will flow better and sound louder. Also, will aftermarket cats throw engine codes and last a long time? Any feedback is great!

Shawn

 

 

I lived in Cali for 21 years. When my cats would go out, I would go down to the local muffler shop and buy a generic cat. The cat was usually around 60, and it would vary whither or not I would install it my self or let them do it.

 

And all cats are high flow cats. Don't buy into the hype for buying high end cats.

 

You can also do the illiegl thing and just gut them. I never did it, but from what I hear you just shove a broom stick up in there and bust up all the stuff and then let it blow out.

Now I have heard on a good running vehicle it will still past Cali smog. But I personally would not take a chance.

 

But like out here in the great state of Oklahoma we don't have any kind of smog testing.

[kroc33]

This just happened to me. I went to my mechanic and he diagnosed it as the cat. My truck has 67k so it was covered under warranty. The dealer took care of it at no cost. My mechanic said that eventually the pieces that break off could clog the exhaust. Then you would be down and out.

[mini1]

Are you sure you aren't just hearing a heat shield or a clamp vibrating? I had a heat sheild go on one of my cars. It just vibrated against the cat, so I just ripped it off. Problem solved.

[hot37shot]

nope! all clamps, pipes, and heat shields are tight. I am positive it is the cats. Now if anyone has aftermarket cats on thier truck and lives in Cali, let me know. I need to know if thoes things will pass smog and if they will cause me to throw codes. OHHH I need to get rid of this rattle! Thanks ppl!

[mini1]

Then you do in-fact need a new cat. If it is rattling then it is nearly dead.

[hondaman74]

Ratteling means the substrate has come loose of the webbing or isulation. You going to need new cats, but cats don't go bad on their own something else causedhte insulation ot burn up. I would make sure hte truck is running right.

[Waterlogd2005]

I don't think I would say that cats never go bad on their own. I know of people it has happened to. Cats heat up and burn off the excess fuel that is released in the exhaust. Sometimes there are small particles of unburnt fuel or gas that are released with the exhaust. It is the Cat's job to burn this off. Through the heating and burning process the metal becomes brittle and can eventually flake off. This doesn't necessarily mean that there is something else wrong.

[hondaman74]

I agree that cats can go bad, but nine out of ten times they go bad due to a running condition. The metals in teh cat Platinumn, piladium and Rhodium do not ever wear out. tehy get coated or contaminated and loose thier ability to convert the HC, CO, and NOX does not dimminsh over time. Tehy will continue for a lifetime unless they are run under abnormal conditions, such as lean, or rich, or misfire are the worst for cats. Cats do not go bad usually, especially the insulation around them. this is usually an indication of extreamly hot condition that hs burned up the fiber glass or metal cushion around hte converter substrate. I would venture to guess that the car is running a little lean or extreamly rich causing hte cats to run hotter than normal in turn buring up the insulation. I would jsut make sure hte truck is running good and the 02 sensors are reacting as normal and staying for around 14.7 under normal conditions. It is all possible that hte O2 sensors are not reacting as well anymore and cuasing hte slow reaction of rich and lean conditions which will also cause the cat to burn up. This is the only reason that O2 sensors flucuate. tehy lean out and richen up to keep the cats happy. Tehy do not like a consistant rich condition, so they will ean it out small amounts to help clean out hte cats as well. Remember we never had O2 sensors until we had cats. Now we use them to help fuel mixture but hte main reason was to help cats do thier job effieciently.

 

Keith

[hot37shot]

Hey ppl thanks for the feedback!

There may be another contributer to my cat going out. In the past with this truck I used fuel additives every 10,000 or so to clean out the system. But this additive was the " Chevron with tetraline" brand, and if I recall the bottle said " safe for all engines". Oh, and my plugs look great too so i dont think the thing is running to rich or lean. At any rate, sounds like I need to replace the damm thing. Funny thing is I just passed smog too, with flying colors. So, if I replace the cats with less expensive aftermarket cats will I pass smog in So Cali.? Compared to the factory ones that are around a grand but will pass smog.

Shawn

[Nytemare]

If you replace the cats with generic stock replacement cats for the afore mentioned 60 bucks a piece and they do not pass smog checks due to the cats being your problem than it is false advertising. Stock replacement cats have one purpose...to act like stock cats. cheeper just means that they wont last as long as your stockers and you may have to replace them every couple years...take quite a few years to total a grand though.