Hi, my 2008 H3-Alpha w/ 123K mi needs some exhaust help. Throwing a P0420 bank-1 cat error, and the original muffler is starting to rust so I'm thinking I like to replace and upgrade the system.
I have read some of the similar posts, and I am considering going dual, and adding some more sound. I see some have eliminated the pre muffler (resonator), but I was not certain if that would be too much noise for the 5.3? Intake is stock, except for a performance filter. I also gathered from the threads that the cats/O2 sensors are finicky (i.e. manufacture specific), is this still the consensus?

I just moved to FL Boca from Texas and I was hoping someone could recommend a custom exhaust shop in my area? I found some that do exotics, but not certain if that translates. I'm sure I be getten the stink eye rollen up in my big fat American Hummer

Thanx!

Bud

 

Here you go, not too far from you= https://www.promufflerdelray.com/

 

Don't confuse what you may have read about I5 H3s with yours, like removing pre-muffler. Take a look under there to see the "problem" with your going true dual idea. You should still keep a cross over for balance even if you find a place make a duel setup. With Alphas, you are going to get a sticker shock for the Cats, like almost a grand for the front pipes alone, and they are getting harder to find.

Finicky sensors? Never heard of that. My 09 Alpha Off Road has more miles than yours, zero issues on Stock front pipes (Pups Cats and secondary Cats) with MagnFlow Cat back, TSP Low Lift Cam, LS6 Springs, one of our Intakes, AFE Filter, SuperModulation PP TB and SFAN 4500 Efan, with my HPTuners tune. One of the keys to not messing up Cats is always running top tier type fuel.

Not looking forward to having any Cat issues, buy probably gonna happen someday. Then I will start that process.

Only the front Pup Cats are monitored, so you could loose the second Cats.
They are both in the front pipes, one just behind the exhaust manifold flange, the second further downstream after the second O2 Bung.


My Motto........... Loud does not mean fast, or power for that matter.

Good luck and please let us know how it goes.

 

I had the 420 code awhile back. The rest of the exhaust system was still in good shape, so I first swapped the right and left O2 sensors to make sure it was the cat and not the O2 sensor. Same code. Decided to try a spark plug anti-fouler on the O2 sensor for that side, and haven't had the problem since. Been at least a few years. I watch my cat temps (with a Torque app) and Bank 1 runs a tad hotter than bank 2, but not enough to cause me any worries.

 

Thank you all for the great information, much appreciated. Looking at the exhaust issue, me thinks I have a bigger issue I should correct before replacing the cats, etc. I am losing about 2-3 quarts of oil in-between oil changes. This is not new, been like this for some time but I want to correct that first. Exhaust tip is black sootty.

Any good chevy engine folks out there in the boca area?

 

Do you know the cause? If you have to diagnose and fix, please post for the rest of us.