I failed emissions when I tried to go through a few years back due to NOx, but not by much. I chalked it up to a POS carb that made my car run like crap. Then in Connecticut they discontinued it for a few years, and I had my car on and off the road (my IROC is my backup/Sunday auto-x car right now).

Anyway, I installed a new carb earlier this year, and just as luck would have it, CT brought back there emissions program. Well, I thought with the carb taken care of, I'd be golden. Holy crap was I wrong....

HC Limit -100, Emissions - 147 = Failed
CO Limit - .32% Emissions - .84% = Failed
NOx Limit - 700ppm Emissions - 1599ppm = Failed Ultra Hardcore

Wires, cap, rotor, plug, air filter all pretty new. Needless to say, I was pretty surprised. However, looking into it a little bit, I found a few things that could have definitely bumped my numbers:

1) Timing too advanced. I noticed under a full load, even with 93 octane fuel, I was knocking. I don't know what the timing WAS set at (I accidentally rotated the distributor before I checked it), but I've now set it to zero.

2) AIR belt was off. Forgot I took this off a while back because the belt looked raggidy and I figured it would give me a horse or something. Picked up a new one and slapped it on.

3) CARB is probably set WAYY to rich. When I installed the new carb, I hooked up a vacuum gauge and adjusted the mixture screws until the vacuum started dropping. This was probably a good 3 or so full turns after the vacuum more or less peaked. For emissions purposes, should I just turn the screws all the way in, or set them to the factory setting? What is the factory setting, like one and a half turns out?

Anything else I can do? The cat is a high-flow catco cat, it's only a 5-6 years old, again with about 15K on it. I'd rather not replace it.

Thanks for the help guys!

 

Reducing the timing should help quite a bit.

I guess I'm in the same boat with my 85' GP LG4.
My 1st tests results:
So after the miserable failure, I bought a timing light because I knew my timing was heavily advanced to make the thing go a little better. Did a few things, set the timing so the mark was "straight up" on the balancer since my motor does not have a timing indicator bunch of parts like new oil, new plugs, new air filter, new pcv, new breather filter pad and put in some 93 octane.

Went back this morning and got the following readings
Not meaning to hijack but wanted to show the effects of the changes I made and also get a recommendation on where to go from here. I don't know if I need to reduce timing some more to get the numbers to all be in place.
CO ? From what I've heard this is due to lack of air in the mixture, Is this from being rich?
Edit: anyone know why this car doesn't have a timing tab?

 

When you say you installed a new carb, do you mean another computer controlled carb, or something else?

Assuming the former: The carb adjustments require a dwell meter and high impedance volt meter. A vacuum gage doesn't tell you much on the computer carbs.

You may need to clean out the EGR passages in the intake manifold. It is pretty common for them to get plugged up, which causes high NOx readings.

 

Sorry, should have been more specific. I replaced my old CC carb with a new CC carb.

Cleaning out the EGR passages - that means pulling the intake manifold, right?

Also, what are the estimated factory settings for those mixture screws, about one and a half turns out?

 

Cleaning the EGR passages requires removing the intake manifold, yes.

The CC carb idle mixture screws have a finer pitch thread, so you need more turns out. When I rebuilt my carb a couple of months ago, the kit directions said to set them at 4-1/2 turns out. Along with the lean stop, rich stop, and idle air bleed setting recommendations, I only had to move the IAB about 1/8 of a turn to get the MCS dwell right after I started it up.

 

Anyone notice that my pass requirements are quite a bit higher than that LG4 GP's???


Update -

Zeroed out my timing, car is running much better now. No more pinging, and a little better low end response. I'm going to leave it at zero for emissions purposes..then set it at something reasonable afterwards.

I don't have a dwell meter at my apartment, so I'm just going to set the mixture screws to the factory setting. They WERE at 5 turns out, and the car seemed to be running rich. You said the carb rebuild kit you have recommended 4-1/2 turns out...how sensitive are these screws? Also, my Chiltons manual recommends 3-3/8...I think I might just set it to that, and see if I get any ping. I figure lean is good if anything for emissions, right? Later I'll pull the dwell meter out and tune the carb to what it should be set at.

Lastly, any thoughts on this...

"go to home depot, run your tank down to a 1/4 tank... buy a half to 1 gallon of denautured alchol... i passed with hollowed out cats on my car, and the carb tuned as normal with a 110lsa cam..."

That's a quote from a guy off a local CT board who's running a thirdgen Firebird, he also said

"add more alchol to get your NOX numbers down...

lean the car out to get your CO numbers down....

do an oil change to get your HC numbers down, but they should generally not be an issue...."

Here's the link if you want to see where I grabbed that from...

http://www.thepike.net/forums/showthread.php?t=7066

I also read somewhere in there that running LOW octane gas is better for emissions purposes because it burns easier...makes sense. Thoughts on this?

 

I did notice. Could be the difference in year or milage. There are some correction factors they use to come up with the values.
Mine is showing 160K but the motor was replaced fresh in 2000.
(Shhh..., I'm not telling)

 

Different states and even different counties within states can have different requirements, based on EPA blackmail. So, you need to know what's required where you need to pass.

In Colorado, the requirements are based on where registered and year of vehicle. Mine is an '82 but the engine/control system is '86 - they tested it as an '82, which is a good thing because the '86 requirements are stiffer, and I would have failed my first two and 4th test (the 3rd was with all new tune-up, and it sailed through).

Anyway, why you might fail:

HC is typically due to unburnt fuel, i.e., a misfire in a cylinder or multiple cylinders. This can be ignition related, or a burnt exhaust valve.

CO is typically due to a rich mixture. Have either of you replaced your O2 sensor?

NOx is due to high combustion chamber temperatures. The EGR is there to reduce those temps - if not functioning properly (such as blocked passages), you can fail. Advanced timing typically has the effect of raising combustion temps, so that's why backing it off can help. Chamber deposits can create hot spots, which will also cause NOx to spike up. Typically, though, timing and fully functioning EGR will do the trick.

 

Never replaced my O2 sensor, and I'm actually fairly sure it's totally gone, or at least faulty at times (with the old carb, used to get an occational CEL, forgot what the code was, but I believe it led me to believe the O2 was gone. Again, this was probably 5-6 years ago, though I only got the code once since I replaced the carb). I would replace the O2 sensor but it's rusted into my exhaust manifold, and I've been told there's no way to get it out. If I'm going to pull the exhaust manifolds off, I'm going to replace them with a pair of headers, but because of Auto-x class restrictions, I can't slap on a header without being bumped up a class, so it's staying as is for now. I've been thinking about having a bung welded into my Y-pipe and putting a sensor in there, however.

I've got an appointment to go through emissions tomorrow morn at 9:30am. I've done pretty much all I can do with the tools and time I've got available. I'm going to add a gallon of denatured alcohol into my tank tonight...from what I've read it'll lean my A/F out and cool my combustion temps, which should help with the NOx and CO. Wish me luck...

 

Good luck, get your timing Waaaayy down and HC and NO should be good.

 

did you pass? where did you get that denatured alcohol? I have no cats and failed but not to bad. I can post my readings. I rather not put cats on this thing. please help

 

I think denatured alcohol is rubbing alcohol sold at local drug stores and walmart.

 

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, should 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.

 

i doubt you'll ever pass without cats.