350Vortec o2 and Exhaust Help

[JB]

I pulled the codes on my 98 Tahoe after the SES light came on yesterday and I get a PO430 code which means that the 'catalyst system efficiency for Bank 2 is below the threshold for the current engine operating conditions". I have determined that Bank 2 is the passenger side exhaust.

There are four sensors under there. I assume all are O2 sensors. There are two before each cat and two after each cat.

What is broke and what needs to be fixed? Sterling GM says $900+, O'reilly's says $400 for the cat and pipe, and all gaskets.(Its all one piece) Bryan Muffler says $200-300 to cut bank 2 cat out and replace with universal unit.

Could it jsut be a fvcked up O2 sensor?

The truck has not been getting the 16mpg (per tank)it usually does. It also seem slightly sluggish.

[stx4wheeler]

i dont know much about all the computers and stuff, but have you checked for some kind of exhaust leak.

[Graystroke]

the easiest way to check to see if the cat is the problem is either with a vacuum test or w/ an infrared temp sensor. check the vacuum and if it is reading low you may have a plugged cat. (remember an engine is basically an air pump. if air can't get out than air can't get in which = low vacum.) also might explain the sluggishness. does it bog or slow on long grades- as if there are any around C.S. this also is a sign of a plugged or broken loose cat.
you can take an infrared temp sensor and take a reading of the temp before and after the cat (make sure engine is at operating temp). if your cat is working right the temp should be higher after the cat than the one measured before.

[stx4wheeler]

yeha i have heard that stuff works pretty good, and if i thought i heard you can use the vacum line off of the brake booster, but i may be wrong.

[uglyota]

Have you tried just pulling all the O2 sensors and cleaning them with non-chlorinated brake cleaner? It may just be a dirty sensor throwing your computer into 'confused' mode.
You could also unhook the pipes behind the cats and just see if one of them looks clogged or burned. Have you overheated? I've heard that can make your catalyst actually melt together and clog it.
I wouldn't get a new one from Ho'reilly for $400...get one at a junkyard

[Graystroke]

do the above test and you don't have to unhook your exhaust! In thirty minutes you could have figured out was wrong and then decided if you wanted to get it fixed (another hour) at the muffler shop or pour that snake oil crap in there. too much "what if's?"and "how many different ways to skin a cat". we're not talking axle swaps...we're talking about an OEM replacement part at worst.

[JB]

Does anyone have a temp sensor or a vaccum tester I could borrow for an afternoon? The vaccuum tester was $25 at NAPA. I know it is cheaper than having someone else do it, but I am being cheap.

I was doubting that it was a really a bad cat but when I went to Aggieland Auto and told them waht the codes told me, he seemed pretty confident that it was the cat and not an O2 sensor.

I looked for the cat cleaner stuff, but couldn't find it. I will try O'reilly's.

It is still very much drivable, but I am pretty anal about keeping this car running as it should. It has 94k on it and as been very well taken care of since we bought it new.

Thanks for the advice.

[JB]

The light went off, but still I ran some stuff through a vaccuum line. It idled like crap for a minute, then I drove it around the block and it idles smoother than it did before.

Why would the light go off if the codes had not been cleared? Does it mean taht it fixed it's self, or do you think it will come back on?

[jerryg79]

the light goes off after like 30 starts if the code hasnt reoccured

I'd get a scanner and clear it and see if it occurs again...sensors get pissed off sometimes

[JB]

I cleared it and it came back. I think I am going to be out some $$. Thanks though for the help.