Hey guys, it has been a long time. I went ahead and read all I could about this problem so I already have a plan but wanted to get any additional advice you guys have.

I failed my emissions test yesterday with the following values:

High Speed (25 mph) (RPM:1637)

__________Standard___________Current
HC(PPM)_____114_______________58
CO(%)_______0.63_____________0.08
CO2(%)_______________________14.7
O2(%)_________________________0.3
NOx(ppm)____796______________1650
Dilution(%)____>6______________14.8

Low Speed (15 mph) (RPM:1574)

__________Standard___________Current
HC(PPM)_____117_______________89
CO(%)_______0.65_____________0.12
CO2(%)_______________________14.5
O2(%)_________________________0.4
NOx(ppm)____879______________1508
Dilution(%)____>6______________14.6

Now the NOx is the obvious high point here. I just had a new cat installed yesterday. It is a small bullet cat that was installed just after my ORY (which might be too far back, though the other values seem ok). I need to check that my EGR is functioning. I currently have a custom tune and can not remember if the shop turned off EGR or not. I have the ALDL cable and will try and check my PCM tonight. I guess I can try this (http://shbox.com/1/4th_gen_EGR.html) as well to see if it is working.

If my EGR is in fact working, my next step would be to either try and put a new tune in myself (buy LT1 edit or TunerCAT) that has a richer A/F mixture or go back to the muffler shop and have 2 cats installed on either side of the ORY (for a total of 2 cats).

Do you guys know of any other checks or easy fixes I could try? I have heard of unatured alcohol in the tank but am not sure where to get that or if it is safe. I drove the car around for a bit before I tested it to try and get the cat hot.

Current exhaust mods are Pacesetter LT's, ORY, hi-flow cat (brand?), Magnaflow cat-back. I have the SLP CAI kit, 52mm TB, custom tune, custom 3k stall converter, and was running 93 octane. Oil was changed right before the test.

Thanks for any help/advice. I have had the car in storage for years and decided to get it up and running (legally). I forgot what a pain these things can be....

 

adding more cats isn't gonna solve your problem. You either have too much timing or a bit too lean.

 

I also had a lot of trouble with emissions..

A big factor is being able to get the cats to "light off" properly and generally with long tubes that requires having them as close as possible to the collectors.. Long tubes dissapate the heat much quicker than a factory set up, this leaving the cats cold and useless

What brand cat do you have? The functionability of most of those "high flow" bullet cats is usually bare minimum.. I actually have a pair of them sitting in the garage right now with less than 500mi on them because I ended up swapping to a better set.

 

The A/F is 14.89 , that is acceptable, richening the mixture won't solve your problem.(http://www.d-tips.com/Tools/toolbox/lambda.aspx) A car with EGR takes car of most of the NOx in the engine and not so much with the cat, I don't think 94 had a three-way catalyst but I could be wrong check your emissions label under the hood, by the word "Catalyst" is should list SFI, AIR, EGR, HO2S and either TWC or OCs(TWC is three way cat the reduces NOx, OC only reduces HC and CO).

If it had a Three way cat, make sure the bullet cat you bought is TWC ,if not that is your problem.

****I just checked the book and it does look like the Camaro/Firebird Vin "P" as having a Three Way Cat, so it does help with NOx even though EGR does most of the work.

 

Thanks 96LS1zee, that is a very cool calculator. What do you mean by Vin "P"? The manufacture year or the engine? I fall into just one of those categories. P = 1993 manufacture year so I wouldn't need that special cat then, but P also mean LT1 depending on the digit. I could actually see either one being true.

****Edit****

Also I must confess. After I decoded my VIN number I realized my car was Canadian. That explains several things I hadn't thought about before. 115mph speedo, 2.73 gears, and everytime I rev it up it makes this weird sound.... VVRROOOM.... EH. hehe

 

Texas has emmision inspection? I had no idea.

 

Sorry to clarify, the 8th digit of the VIN is related to the engine. P being the 5.7 LT1, the other option would be K, which is the 3.8.

 

Lol yeah it's a shock but it's one of like 22 states that actually do emissions testing. Always a pain to deal with when you've got hopped up cars pre-96.

Edit-Not all counties have emissions testing though I just happened to live in one that does...last I heard there were only like 4 counties that actually do it...although I can't actually verify that...just what I've heard.

 

Those little bullet cats, like muffler shops sell, ain't much. Factory cats are much cleaner. I doubt backing the timing up is going to help, your HC is not high. Excessive timing raises HC. Late timing lowers HC but raises NOX. EGR is likely not functioning. EGR ( or more EGR ) would likely help. Just driving around won't likely put enough heat in those cats to do much good. Run it hard at highway speeds would do more good. Keeping the factory cats is always smart when you have to pass smog.

 

All f-bodies are Canadian.

 

Yep, first digit in the vin is 2. :-)

 

Learn something new every day.

I downloaded the trail TunerCAT software and have my cable. I emailed the guy about a trial copy of the $EE definition but I haven't got a response yet. I haven't had time to check the EGR manually but I will try to check the computer today if I can get that definition file or at the latest I'll check it manually Friday.

Thanks for the help and responses guys!

 

I ran into trouble getting the EGR to function with PS LT's because there isn't enough back pressure to get the valve to operate. As said above make sure the cat is a three way or it doesn't have any effect on Nox. Once I changed out the cam it created its own egr function and I had no more problems getting it to pass.

 

Here's how you pass emissions testing... Move to a state without them! haha.. no really though, if you ever get tired of it all, maybe you could register your car somewhere that they dont test. You'll need a family member or GOOD friend that lives in one of these places though that will aid and abide your sidestepping ways... I did it when I was in California for 2 and 1/2 years.

 

I failed the CA sniff test, replaced the EGR, and still failed with two different aftermarket cats. Found a brand new (never installed) OEM cat on this site from a 2010 posting and passed with almost 0% NO.

 

Hmmm.... Maybe I'll have to do that. I'll try the EGR today. TunerCat got back to me and I got the trial for the $EE definitions so I will load it up tonight and see what I can find out. Hopefully I can get some check the EGR and turn it on (if it is off) and get it tested today to see. If not I'll have to take the cat back to the shop and have them replace it with a triple catalyst type one or install a stock one.

 

My sister's 94 had this problem. We had to do a new factory replacement cat. Tune up, new egr valve, and put it back to stock manifolds and y pipe. It had mids with a cat in the factory place but still wouldn't pass until we put the stock manifolds back on.