Took a trip and came back with a new project

[Thumper8302]

So i decided to go see a buddy that lived a few hours away from me yesterday. As soon as i exited off the highway and stopped at the light my kon started to idle rough for like 2 seconds and then throw the check engine light... Its only idled funny on me 2 times in the last 160 miles.... Went to autozone and pulled code P0430.... Catalyst issue on bank 2 which is the passenger side... Gonna take it past the muffler shop and see what they can do for me... Now my questions for all of u.. 1st thing 1st its a 2001 yukon, 229,***, all stock 5.3l, 2wd. My ecbm is out as well... Now i looked up some parts last night and noticed the stock cat part is around $455 considering it is the complete y pipe with 2 cats. Now i was wondering if it would be wise to replace the whole thing or could just buying 2 hi flow cats and cutting out the old ones be a wise decision? Kinda in a pinch for cash considering i just bout this vehicle not even 3 months ago. Any advice on my situation would be great.. Just not sure on which route would be the better of the 2... Im also goin to prolly be looking at getting all 4 o2 sensors replaced as well... Much appreciated guys

 

[cam3439]

Well I replaced all 4 O2 sensors and it costed about $250 (just an FYI). Even though they were kinda expensive for O2 sensors, they really smoothed out the engine at all speeds (so I recommend them). As for the high-flow cats, I would do some research on this because some vehicles tend to start throwing codes with the rear O2 sensors. My friend with a 2007 Monte Carlo SS put one on and had to turn off his rear O2 sensor since it would always throw a code (after about 2 weeks of having installed the high-flow cat). I guess wait for someone that has put some high-flow cats to chim in. Whatever you do I would just cut the old ones off and replace them with the new ones.

 

[Thumper8302]

im not sure if im following u right.. he turned off his rear o2 sensors? are they not there for a reason? IMO... but what ive learned and heard about a quad set of o2 sensors is that the front set has a read out of a roller coaster "look" and the rear set is more of a constant flow...

front---- looks like our heart beat
rear---- looks like a nice even flowing wave

and also IMO the rear set is also used to be able to tell the computer if the the cats are doing their job or not....

but back to the topic as far as replacing the cats.... would it be better to replace with the stock y pipe or just do a chop & weld? also thinkin down the road of installing some long tubes which im sure will involve some chopping of the y pipe....

 

[cam3439]

He has a 2007 Monte Carlo SS (5.3L) and it only has 2 O2 sensor on it. The rear started to throw codes with the installation of the high-flow cat, so he disabled it with an HP tuner. And yes, the rears tell the computer if the cats are doing a good job, and the fronts tell the computer if you're too rich or too lean. I THINK that the high-flow cat steps into parameters outside of what the stock tune is set to and thinks that there is something wrong with the cat. The codes would come on and then turn off and then turn on and so forth, so he disabled it and just has the front one on. This is the problem that i'm talking about. I don't know if you'll have the same effects, but it is something to consider/look into. If you get a new set, then other than burning oil or running too rich (which is a problem that you didn't directly cause), stay away from fuel additives like octane boosters since they damage the O2 sensors and cats. For now I would just replace the cat itself and not the whole y-pipe setup. If you install long tubes later they're just going to chop up the front of the y-pipe and you would have paid all that for nothing. Personally, I would try to get the exhaust shop to try to mig weld most, if not all, of the cats on.

 

[Z-56 Hoe]

I have a 2001 Tahoe and have the Dynatech Long Tube Free flow Headers with Free Flow Cats and Y pipe its a whole set for about $1400.00 but its so worth it I couldnt be happier with that part.

 

[Thumper8302]

thanks for both of ur all info... went to the muffler shop today and they said that before i go replacing the cats i should go to my TRUSTED mechanic to try and see if anything else might be the issue. Told me the alot of misc crap can wind up throwin up a code for ex, a thermostat, needing a tunupe, filters, small oil and exhaust leaks yada yada yada i thnk u all get the point.. so off to my mechanic i go... got to talkin a lil bit and he said very doubtfully that it could be my cat and might just be an o2 sensor... so we r going to be goin that route today he. he thinks is the pass rear. so hopefully the cats are good and i can just save up and go with a completely new header back exhaust when the time comes.... will keep u all informed on what all happens

 

[ryangt]

The ONLY time my yukon has ever thrown a code at me was a "lean mix" code suggesting an 02 sensor issue. I was furious because i was hmm about 500km into the middle of the effin aussie outback. I looked under the hood and it was simply the k&n intake pipe had wiggled loose off the throttle body due to all the corrigated roads around here.

The point is, i spent over 10 min looking around under the hood to find the issue and it was staring me in the face the whole time. It could be anything so i would double check EVERYTHING in the intake track and make sure its not something loose, just to be sure and save $$$

 

[dwmmatt23]

im having a problem with a p0420 code and from what everyone has told me that the p0420 and p0430 codes are only going to tell you the cat is not working, if the sensor was bad it would be a different code or none all. i just have to take the fact that i have to replace both cats at 90k miles

 

[Eagle]

if your cat was clogged it wouldn;t have run on the freeway.

if your cat was failed it would have thrown the code ON the freeway during closed loop steady state driving.


the code actually has to do with the 02 sensors, not the cats themselves. I'd guess one of the o2s is on the way out (sluggish).

 

[Thumper8302]

if your cat was clogged it wouldn;t have run on the freeway.

if your cat was failed it would have thrown the code ON the freeway during closed loop steady state driving.


the code actually has to do with the 02 sensors, not the cats themselves. I'd guess one of the o2s is on the way out (sluggish).

i agree with eagle on all of that... if a cat is clogged ur car will more than likely overheat.... on our trucks from what i have heard from both my mechanic and an exhaust shop is that the front o2s control about 80% of ur rich or lean lean mixes... rears control the latter 20% and also inform the computer if ur cats are functioning... now ill have to read the code report again but from what my mechanic was sayin that Catalyst System Efficiency Below Threshold typically means its downstream on both the p0420 & 30 codes... which in the case is the rear o2 sensors.. will be takin it in the shop in the mornin... keep u all updated