Hi all,

I have a 2002 3.8L auto camaro with 21,000 miles on it. It has a K&N air filter and as far as I can tell that is the only mod. I get a service engine soon light. I had autozone check the codes and it says the cat is bad. It also says there may be reasons for that like vacuum leaks and misfires. Anyway, If I clear the code, the light will stay off for 50 or 60 miles and the car runs great. Then for no apparent reason, the service engine soon light comes on. So far, I have cleaned and re-oiled teh air filter, changed the oil and filter and replaced teh spark plug wires with Bosch spiral core wires. I have also looked for vacum leaks and have found none. Before I go spending a small fortune on the cat, is there anything else I can try?

 

The code for a bad cat is 98% accurate so long as there is no O2 sensor codes at the same time. If the cat is bad don't let it go for too long it can cause other issues as well.

Get the cat replaced if there were no O2 codes. Replace the O2 sensors if they have codes and see if the cat code comes back. Or have an exhaust shop check your cat out for you to know for sure

Massey

 

one of my cars was throwing a "bad catalyst" error and I cleared it a few times waiting and sure enough, the O2 sensor eventually threw its' code. I replaced the rear O2 and haven't heard a peep since.

 

Don't automatically assume your cat is bad and take it in to get replaced right away. If the cat really isn't bad, that could leave you with less than happier results; a drained wallet for nothing. A bad cat condition is read (or misread) by the rear 02 sensor, with the system comparing the front to rear sensor readings. A fouled sensor will give an off reading, throwing a catalyst error, but not necessarily be considered "bad" as far as throwing an 02 sensor code is concerned. You can check if there is a restriction by hooking up a gauge to the pre and post cat 02 bung holes (go ahead t.i.g., have a field day) one at a time, and see what the difference between them is. The front will be a little higher due to the natural slight flow restriction of the cat. A huge difference means there is a considerable restriction. I prefer the drop it from the flange method to take a peek inside. At least then you'll be able to inspect the integrity of the cat's innards.

 

I am curious, what other problems would be caused by a Cat not cleaning the exhaust enough?

 

I think he was reefering to if the cat was clogged/restricted.
Back-feeding into the EGR is the only thing I can think of, in addition to poor engine performance or stalling.

 

good advice and it's why I was in no hurry to replace the cat on my vehicle in question. After a couple months the O2 revealed itself and I've seen no more Catalyst errors

about the innards of the cat: I don't have that problem. My cat tends to dump his innards on my rug, bed and even on the couch.

 

A cat like that wouldn't last long in my house before getting gutted....through the bung hole! lol

 

Plugged or reduce flow cats will not normally throw a "Cat" related code. I assumed the Cat code was Cat low efficiency code. Normally they throw these codes once the cat falls apart internally. (or a sensor issue, like you said) The only negative side to this is they tend to rattle going over bumps. I guess the pieces could become plugged but most of the time people come in for the check engine light. A tap on the Cat confirms the failer and it get replaced. In theroy you could just remove those pcs of Cat and run the car with that code, there is really no down side unless you care about tress or your kids future.

I do not advise this because I have heard of it leading to massive uncontrolable horse power gains making the car almost undrivable.

 

Clogged cats will cause the upstream o2 sensor to fail, burn up the egr valve, and cause drivability issues that can be a pain to diagnose correctly. Codes for the MAF and MAP can also be thrown due to excessive exhaust in the intake if the egr valve is stuck open.

The cat can still be clogged even if it does not rattle. I had a car that could not make a top speed of 45 because of the cat being so clogged. No rattling but lots of melted honeycomb inside. Take it to an exhaust shop if you are unsure how to check it yourself.

Massey