Are My Cat's Blocked?
 

So, here's the symptoms of my 2002 CE T/A as of the last couple of months:

1. SES light is on
2. Below average fuel economy
3. Below average performance
4. Exhaust has gotten crazy loud
5. Very rarely, a brief rotten egg smell

All of these from what I've read can be associated with blocked cat's, and now I just used my Scantool and Torque app to pull the codes, and here's what I'm getting:

All signs seem to point to the cat's being blocked but they're a pain to get off with the lack of space and they aren't cheap so I'd like to be certain before I do anything. Does ANYONE object to my diagnosis?

Also, what can I do about those air injection system codes? Does the whole pump need to be replaced or is it just one of the valves? I still don't fully understand that stupid thing.

That would be my best guess, especially with the rotten egg smell... I would wait for some more opinions though!

-Garrett

I would not expect the exhaust to get louder if the cats were blocked.

Is the engine still able to rev into the higher rpm range? Or does it "hit a wall" at a certain rpm?

Have you measured the surface temp of the cats with an IR gun?

Lots of other things can cause the symptoms you are describing. Several O2 codes are present, and faulty front O2 sensors can certainly causing poor A/F and thus poor performance, poor MPG, and that "rotten egg" smell that comes with an overly rich A/F as it passes through the cats. I see that you have codes present for front AND rear O2s, so perhaps a wiring issue is also worth looking at here.

Contrary to popular belief, there are no codes that directly indicate a clogged cat. These codes....

P0420: Catalyst System Efficiency Below Threshold (Bank 1)
P0430: Catalyst System Efficiency Below Threshold (Bank 2)

....simply indicate that the oxygen storage capacity of the cats is reduced or eliminated, as determined by the difference between front and rear O2 sensor readings. You would see these same codes if you were to remove the cats completely and not disable them with tuning or O2 sims. As such, they don't automatically indicate a clog, but they don't rule it out either. Sometimes the coatings wear off the substrate and the cats become a pass-thru that still flow fine but no longer provide the intended reduction in tail pipe emissions (common issue on the '00-'02 LS1 F-bodies, GM issued a TSB about this and extended the warranty for this item).

Hmm. Well, all the o2 sensors were replaced in the last 6 months with AC Delco ones. Also it's only the rear mounted ones throwing codes.

I have not checked the temperature with an IR gun, primarily because I don't have one, but I can tell you that when the wind blows by, the temperature of the air coming from underneath the car is insanely hot, it wasn't this way until about the same time as the other symptoms.

The trouble codes there to tell you there are faults, repair the system faults as indicated. The only test for blocked cats is a back pressure test at the AIR fitting on the exhaust manifold.

I'm guessing you have no idea what to do to repair the trouble codes? The rotten egg smell is the cat overloaded with fuel, as it burns it off you can smell the sulfur in the fuel. Doesn't mean the cat blocked or ruined YET, but let go it will ruin the cats.

Ah, well I haven't smelled it for at least a month now, and the last month is when the rest of the symptoms have gotten really really bad. Is it likely that that has happened?

Not based on your initial post. P1153 - HO2S Insufficient Switching Bank 2 Sensor 1 (front passenger side O2 sensor).

I would start with this issue and work from there. Replacing cats would be a mistake if there is still an underlying issue that ends up damaging the new ones as well.

Exactly. There is no smell that indicates a clog either. But an overly rich mixture can dump enough fuel into the cats to cause overheating and damage/melting.

Check the fuse for the 02 sensor heater circuits, if that's ok check the wiring.


Also replace both AIR check valves on the exhaust manifolds. That will fix the po1415 code

1. SES light is on
2. Below average fuel economy
3. Below average performance
4. Exhaust has gotten crazy loud
5. Very rarely, a brief rotten egg smell

If the exhaust has gotten noticeably louder that tell me at least one of your "cats" is already damaged and lost a large portion of the brick inside it. So most likely you'll need at least one new "cat", but before installing new "cats" you need fix the rich/lean condition first.

Oh, something else I forgot to mention. It's been backfiring on a cold start for several years now. Not sure how that can affect the cat's but it can't be good.