Cat or O2?

[TogaPC]

So here's the deal. For a while now I've been unhappy with the way my truck is running. When it's cool outside it runs great but when it's hot it tends to bog down and seems sluggish. At times it even fails to accelerate under heavy throttle. I've been taking it easy and doing some troubleshooting but without a code all I could really do was speculate. The exhaust has been sounding weird too, almost like the engine is missing but there is no vibration from the engine.

Finally today the check engine light came on. It's a P0420 so I'm pretty sure it's the cat or O2 sensor. My question to you guys is, are there any tricks to figuring out which it is. I'm kinda leaning toward the Cat but like I said they are expensive.

I tried banging on the cat but I didn't hear any rattles. Tried checking the temp of the pipe before and after the pipe. Behind the cat was a little hotter. What's next?

P.S. If anyone in the Austin area has the tools, the knowledge and the willingness to help a brother out, please PM me.

Edit: BTW. Which side is bank 1?

 

[blueflamed03]

if you replace one side, I would replace both...you can get both fronts from Rockauto for about $70 each side...replace just the fronts, and see what that does. Loosing at 02 can cause loss of power, and bad gas mileage.

 

[Volant1]

If you think its the sensor swap them with the otherside and see if the code jumps to bank 2, bank 1 is the drivers side on the tahoes, all you need is a wrench 3/4 if I remember

 

[TogaPC]

More pressing issues have arisen. Truck is in the transmission shop today. Not sure what's wrong but I'm sure it's not going to be cheap.

 

[blueflamed03]

wow...no, never are, sorry man

 

[TogaPC]

Looks like a cracked sun shell. Tranny needs a rebuild. Oh well, at least now I don't have to worry about it for a while.

On with the exhaust issue though. I saw a Y-pipe with cats on rock auto for under $400 bucks. No welding and much cheaper than the $800 I was quoted from a shop. Anyone know of any issues with these types of replacements?

 

[blueflamed03]

wow...thought of headers and NO cats?

 

[TogaPC]

wow...thought of headers and NO cats?

I've thought about it but 1. it's illegal, 2. there is only marginal if any performance gian and 3. it's louder. I'm also worried about it negatively affecting back pressure.

Please correct me if I'm mistaken. No cats is def the cheapest option.

 

[blueflamed03]

yes, then tune out the rear 02's, but in Austin, your right, dont think you can get around that.

 

[TogaPC]

Sorry it took so long to update but I finally got my drivers side cat replaced. The guy that did the work for me drilled a little hole in the pipe in front of the cat and stuck a pressure gauge in there and watched the pressure at 3000 rpm. The pressure rose significantly on the drivers side and non on the passenger side. When he cut the drivers side cat off he showed it to me and it was almost completely blocked. Put a OEM replacement on it and the truck is like new again. Ooodles of power and it sounds awesome again. Made me remember why I paid the $$$ for the Corsa Sport CBE.

It does concern me that the one cat was clogged so bad like that. He said that it could be the result of a fouled spark plug or a head gasket leaking water or oil into the combustion chamber but since my vehicle does not use oiil or water and runs so smooth he didn't think any of that was the case.

Anyone else got any ideas?

BTW...Tranny was completely rebuilt and reinforced with all the little aftermarket goodies that everyone brags about so much on here. So far it's been a real treat to drive and it came with a 12 month warranty. Shifts are snappy and confident and now that the EFI system is working like it's supposed to the old girl is fun to drive again.

Not sure if anyone is in the Austin area, but I can't say enough about Longhorn Transmission. They shot me straight and have been very honest and fair with me every time I've used them. After this trans rebuild I will never use another shop. Also American Muffler in Liberty Hill is fan-effin-tastic. It's just this older guy with a little two bay shop that he built. He's been doing exhaust for 27 years and knows his stuff. He actually turned me away from replacing both cats and did the test to show me the other cat was fine. We had a good chat while he worked and it got a sense that he really loves what he does. He is ultra friendly and is willing to go the extra mile to help you out.

Highly recommend both shops if you need work done.