Hi All,
I need you help please. My car just fail emissions today. I have a print out copy attached of why. The can runs great, healthy for the most part, but i gutted out my center CAT a while back ago and left the other two cats under the headers alone. this is why it's failing. is there anything at all i can do to get it to pass with out buy a new cat? I have access to my chip and can make many changes. What can i do to get a pure pass without buying a cat. I'm trying to hold off on the cat because i want to save up for a full exhaust system this coming summer.

BTW i tested it with my stock factory chip..

 

you have 3 cats? other than ford, i don't remember the older cars having more than 2 cats, but then i don't work on many vetts.

CO is how much fuel your motor is getting, the higher the CO is, the richer the mixture.
if the CO is too high or too low, the HC will go up, lowering the CO will also cause the NOx to go up.
lowering the timing a little may drop the HC & NOX some, but it normally doesn't have much of an effect on CO.

your CO looks pretty good for gutted cats. i don't think you will be able to get the CO where they want it without a good working cat unless you know someone who has a 5 gas & will let you use it to tune with, but even then i think it will be hard to get the CO down that much without both the HC & NOx going up out of the limits.
maybe go ahead & get the cats you want & temporarily put them on to pass & then pull them back off.

 

Yeah man i think i'm gonna do that advance auto $71. So i'll do this. I'll buy the CAT. put it on for a test then pull it off. If i gut the other two smaller cats and test it two years later with just the big cat will it pass you think? That way i'll totally be cat free,until the next test.

 

there is nothing wrong with using just 1 cat, as long as its big enough for the motor & its a quality cat. there are alot of aftermarket cats out there that just won't work as good as they should.
i have seen some that did a good job on CO & HC but would only reduce NOx by 10 PPM, there are others that do good on NOx but don't do very good with HC. find out who makes the cat & if they have any problems with reduction, a search on the net may help with that.
i don't know if they will sell them or not, but if they do, a trip to the wrecking yard & get one off a low mileage late model pickup to use just for testing may work.

 

I was using this as a guide to what was wrong when I was going through this on my LG4.
Reducing the timing will help with the HC and you can play with the AFR to try to get the others in line (as best as you can anyway)
Yes I know it says Toy.. on it

Almost forgot, When it runs with allot less power you're getting closer. Don't try to make it be snappy off the line. After the 4th test my car sucked for power but it passed. I upped the timing as soon as I left the test station

 

I just had to pass an IM240 dyno test. I found that I could cut most of the readings in half by backing the timing off 4-6°. BUT my tune wasn't that close yet but I had to run it anyway.

 

can you guys give me advice on what to do please. Keep in mind i have no cats. I'd like to keep it that way too, sould i get denatrual alchol and retard timing 4-6 cross the board in my chip, and lean my fuel out by 3%. or is it a waste of time and easyer to put a cat on it. guess what i'm trying to ask is is it possable to pass emission with no cats.

I have my results here that will help you'll see how far or close i am

 

Without a oxidation catalyst (the 2nd brick in a cat) I doubt you'll get below the CO% limit.
Get a cheap universal cat, get 2 stainless band clamps and "geeterrr donnne" or waste the same money on chemicals for the gas tank that won't be as effective.

 

thats all i need to know, I'll get er done today. I found a hot swap cat for about $130 from advance auto i'll put her on pass it then move with my life. Emissions testing SUCKS can't wait to get the hell out VA.