Z28_1991_Camaro

I failed my emissions test twice and I cant figure out why...I've attached my results.
I have a 91 z28 tpi, 5.7.

The 1st time it failed I hadn't done anything to the car other than an oil change. Once it failed I looked online as to what could cause a NO ppm failure.

I changed my pcv valve, distributor cap and rotor.
My timing is set at 6 btdc.
I checked the egr valve the best way I could. I started the car and let it warm up to operating temperature and I had my uncle feeling to see if the egr valve moved when I shut the engine off and he said it did so Im assuming its functioning properly.
I tested a 2nd time and it failed worse and also failed the HC ppm category.

I purchased a new o2 sensor but I havent installed it yet because from what I've read online that shouldnt have an impact on the NO count.

I swapped my 305 for a 350 a couple years back. Does the 350 produce more pollution?
My dad brought the car to be tested both times and he wouldnt have told the testers about the bigger engine being in the vehicle.
When I did the swap I had an emissions test done at that time and I passed. I remember it barely passed but I dont remember which categories were close to failing. My dad brought the car to be tested back then as well and I doubt he would have said anything about the engine size.
The engine was pretty much cold when he brought it both times this year. I've read that would be better for the NO category.

I always run 94 octane fuel in the car.

I also have one of my fans on my radiator wired to run at all times...that wouldnt affect emissions would it?

I don't know what else to try? Anyone have any suggestions for me?

camaro3554gear

iTrader: (2)

what condition is your CAT? If all of the internals have broken down and blown out the exhaust it will definetly cause the car to fail emissions testing. Also I would install the new 02 sensor, the sensor in your car could be switching slowly (lazy sensor) this can also contribute to higher emission gas levels.

Z28_1991_Camaro

If i remember correctly the cat is somewhere between 2 and 3 years old

firebirdman

like camaro gear said what is your cat like? Try changing your spark plugs they will burn hotter and get rid of more gas. change your air filter.

camaro3554gear

iTrader: (2)

is it an aftermarket cat, or was it replaced with a GM cat?

Z28_1991_Camaro

I believe it's an aftermarket cat.

The sparkplugs have about 13000km on them, they normally would last much longer than that wouldnt they?

camaro3554gear

iTrader: (2)

if its aftermarket its probably bad, they don't last very long. I also agree with firebirdman, I would change the plugs and air filter.

Z28_1991_Camaro

Im hesitant to replace the cat because if im not mistaken this will be the last emissions test I would ever have to do on my car. Once I pass the stupid thing I was going to take my cat out completely.

My air filters are kinda dirty, I was going to buy a k&n recharge kit tomorrow. Could dirty air filters really have a big impact on the test?

camaro3554gear

iTrader: (2)

absolutely, dirty airfilters restrict clean airflow into the engine. An efficient clean running engine needs clean intake air

Z28_1991_Camaro

Would I be better off to just take the air filters out for the test?

camaro3554gear

iTrader: (2)

no because then your not filtering out the small dirt particles in the air going into the engine. If you have K&N filters just clean and oil them

Z28_1991_Camaro

I will do that.

Is there anyway to test my cat to see if it's still good?

camaro3554gear

iTrader: (2)

you can measure the inlet temp on the cat then measure the outlet temp of the cat. a properly functioning cat will have a higher outlet temp, usually a noticeably higher then the inlet temp. if the temps are the same, the cat is hollow, if the inlet is hotter then the outlet, the cat is not working properly. I use a snap on laser temp gun to measure the temps. I know there is at least one more way to test them, but it slipped my mind, lol.

Levman74

The engine should be up to operating temp when you bring it in, engines run their dirtiest when they are cold, and especially when the cat isn't hot. Also, not sure why you are running such a high octane fuel, but at least drop down to 91 octane, that will help speed the burn up, but if you were having detonation issues, ignore that piece of advice.

I H8 WWD

iTrader: (5)

I would say lower your octane, install the new o2 sensor, get a new cat (new is like $50-60). Drive the car a good hour or so before you go to let it reach at least 180* constant (remember they will put a fan in front of the car so it will cool your car down even more when they test, so its like your car is running probably around 150* when they test it, as you have your fan plus their fan on).

Replace what needs be one last time, then sell the cat for like $35-40 or something if need be.

RFmaster

Judging by attached numbers you are running slightly rich mixture. NOX values go up dramatically when you have lean mixtures, but also increase as you move to richer mixture, away from the 14.7:1. It also appears that you may one or two cylinders misfiring as evidenced by elevated HC levels at idle and 40kph. Your CAT is fine since CO% are very low.
During incomplete cylinder fire intake mixture gets dumped into exhaust. Some of unburned HC can be converted by the CAT, but excess O2 gets by and detected by the NBO. ECM sees higher O2 levels and richens mixture to compensate increasing O2 levels which increases HC levels even more. Your 3-way CAT has to perform the following three tasks:
1. Nitrogen oxides reduced to nitrogen and oxygen: 2NOx → xO2 + N2
2. Carbon monoxide oxidized to carbon dioxide: 2CO + O2 → 2CO2
3. Unburnt hydrocarbons (HC) are oxidized to carbon dioxide and water: CxH2x+2 + 2xO2 → xCO2 + 2xH2O

Check your ignition components: spark plugs, wires, dizy, rotor & coil

//RF

tony_cogliandro

iTrader: (3)

what do you mean its the last time you have to get a smog test? what planet do you live on?
in Cal if you get a cat after 1-1-09 you have to buy the obdII cat even if your car is an OBDI. cost you about 120.00.
and keep the cat on - it does not cost much HP and should keep the air clean. good aftermarket cat is magnaflow.

I H8 WWD

iTrader: (5)

In my county we have a 25yr stand where once your car hits 25yr's old we can get historical or collector plates, which means we no longer need to take an emissions test. So where he is at it seems they still have the 20yr rule (my county used to but raised it to 25yr's) which would mean on Jan1 2011 his car will be emissions exempt, meaning no more emissions test whatsoever.

I am emissions exempt 2014. 2 years after we all die...haha just playing. But my car will pass emissions already without all the emissions parts, its why I removed mine, if it passes without, why have them then. But lets not get into a dispute about that, I know how you Cali guys are.

Stephen

iTrader: (12)

In Texas, its 23 years.

Just because testing isn't required, doesn't mean we can just rip off all the smog stuff. It would still hafta be there, to pass the Visual Test. Doesn't mean it has to function or the cat can't be hollow, but it does have to be there.

But really.....A good system costs you what? 3hp? 5hp? That is the same as a variance between dyno runs. And can cost you $$$$ for tampering with equipment, if they decide to pursue & prosecute a person for tampering.

pearl_iroc

you gotta do e test for the rest of the vehicles life(1988+) here in Ontario, unless when it turns 30 you can apply for classic vehicle and if your approved then youd be exempt, also you dont wanna get pulled over and they see no can and get like a 400 dollar fine!

Z28_1991_Camaro

Does it make sense that after I changed the cap and rotor after my first fail that my numbers actually got worse on the 2nd test?

I purchased new spark plugs, Im going to try and get them installed on the weekend.
I'm going to see about getting some new wires as well.

To the best of my knowledge, once the car is 20 years old we no longer need to get them tested here. I was planning on taking the cat to work and drilling it out, I wasnt going to remove it completely.
Also, cats are not $50-60 over here. The last one I bought I think was almost $300...that's why I'm hesitant to change it.

How would I go about checking if any of the cylinders are misfiring?
I ordered a laser temp gun from ebay, Im hoping to get it by the weekend. If I pointed that at each cylinder, would the temp be significantly different if there was a misfiring issue?

Also, I'm running 94 octane because when I had my chip made when I did my engine swap it was programmed for premium fuel. There is a noticable difference on how the engine runs with 91 and 94 octane.

Z28_1991_Camaro

I just looked it up, it appears they changed the law so iroc is correct, it's got to be an 88 or older for the 20 year rule to apply

Z28_1991_Camaro

So I'm going to change my spark plugs and wires tomorrow and clean my air filter.
If the place is open I'm going to bring it in for another emissions test.
Do I go with a hot or cold engine though seeing as how I'm failing the NO category the worst?

I H8 WWD

iTrader: (5)

Always make sure the car is up to operating temperature, around 180* at least, but around 210* would be better. My brother ran his through the emissions test WITH BLOWN VALVE SEALS at around 220* and he almost passed (failed by 10 or so points in that category). These motors were made to run hot, and by hot I mean up to 230* before secondary fans turn on (IIRC its more around 245* the second fan turns on but you understand what I mean).

Z28_1991_Camaro

I failed my emissions test again after changing my o2 sensor, spark plugs, wires, pcv valve and cap and rotor.
I failed the NO ppm category again. I got a reading of 1270 when the limit is 632. 1270 is the highest reading I got so far out of my 3 tests.

The only thing left to change would be the cat.

The girl at the front desk told me there are basically 2 types of cats, cheap ones and good ones...she said something about cones?

How do I know if I'm getting a "good" one.

I H8 WWD

iTrader: (5)

Buy name brand

Catco, Magnaflow are GREAT QUALITY brands. Look for a 3-way cat.

Two-way

A two-way catalytic converter has two simultaneous tasks:

1. Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
2. Oxidation of unburnt hydrocarbons (unburnt and partially-burnt fuel) to carbon dioxide and water: CxH2x+2 + 2xO2 → xCO2 + 2xH2O (a combustion reaction)

This type of catalytic converter is widely used on diesel engines to reduce hydrocarbon and carbon monoxide emissions. They were also used on spark ignition (gasoline) engines in USA market automobiles through 1981, when the two-way converter's inability to control NOx led to its supersession by three-way converters.

Three-way

Since 1981, three-way catalytic converters have been used in vehicle emission control systems in North America and many other countries on roadgoing vehicles. A three-way catalytic converter has three simultaneous tasks:

1. Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx → xO2 + N2
2. Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
3. Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: CxH2x+2 + 2xO2 → xCO2 + 2xH2O

Z28_1991_Camaro

I called a local GM dealership and they wanted $650 for a new cat...the guy I spoke with then proceeded to tell me that they were discontinued and he could not get one for me.

I called a local part store.
They want $153 for a Maremont brand cat. Is Maremont a good brand?

I live in a border city so I can drive to Michigan if I need to in order to buy parts there.

Can someone suggest which would be a good choice for me. I'm thinking Advance Auto Parts or Autozone would be the way to go. Here are links to their cats:

http://shop.advanceautoparts.com/web...R%7CGRPEXHAAMS___

http://www.autozone.com/autozone/cat...entId=cat30069

In case the links don't work properly, I'm looking for a cat for a 91 z28 5.0L.

Z28_1991_Camaro

I called 2 more local places today and they both only carry Maremont.

I've never heard of Maremont before. Do they make half decent products?

pearl_iroc

do you have a Performance Improvements store near by ? i got my magnaflow from them for about 120 ish i thnk with tax and have done the last 2 etsest with it on and have had no problem (usually i do 2 speed idle tho) cuz the place i go to has a drive on ramp and my car is to low to fit on it.

I H8 WWD

iTrader: (5)

DO NOT buy Maremont, sounds like a Hospital name lol.

This is the emissions compatible version of my catalytic converter

http://www.jegs.com/i/Magnaflow/642/94119/10002/-1
NOTE: Summit Racing does not have this part.

This is the EXACT one I bought

http://store.summitracing.com/partde...5&autoview=sku

Z28_1991_Camaro

There is no Performance Improvemtents around here.
I called a performance parts store today as well but the guy isnt sure if the cat he sells will pass emissions.

I went to the Jegs and Summit racing sites and when I enter my car in the vehicle search the only cats that come up are made by dynomax

I H8 WWD

iTrader: (5)

A lot of cats aren't put under each cars specifications. A universal cat will work just the same. Just find one with an air tube, is a 3-way, is close to stock size (as far as length and inlet/outlet size goes) and go for it. Just don't buy any off brand parts.

If anything, go to google type in the name of the company and 'review' after it (Ex: Maremont review) and you should find reviews on that company whether from review sites or comments in other forums.

P.S. Dynomax is okay in my book as well.

Z28_1991_Camaro

http://www.ws6project.com/user_stor/...roducts_id=509

Ever heard of Random Technology? If it meets California requirements it should be more than adequate for what I need right?

I'll do some googling later on when I have some more time.

BlackMamba

iTrader: (6)

do you think that California has a law like that, that once your car hits a certain age it doesn't require a emission test.

Z28_1991_Camaro

I replaced my cat this past weekend. I have an appointment for another emissions test tomorrow morning.

I was wondering what exactly the air tube on the cat does?
Also, does it need to be an air tight fit to function properly?

I have a rubber hose on it now, one end of the hose seals off completely but the other end does not. Would that be a cause for concern?

paulo57509

Why throw unknowns into the mix?

The AIR tube is air tight from the factory. Why not do it right and do the same?

If you have enough tube length to use one toss the rubber hose (it'll eventually burn away anyway) and use a 1/2" tube compression union. Stainless would be preferablem but a brass hardware store union will work in a pinch.

The AIR tube provides secondary air to the cat. I think it allows the cat to further process the exhaust gases because of the extra air that's being provided by the AIR pump. This is one reason why you cannot use the presence of O2 that's on the emissions test read out to tell if your mixture is lean or not. There will always be excess air showing up on the print out.

Z28_1991_Camaro

The rubber has been on there for about 3 years and it appears to be in excellent condition.
The rubber hose isnt big enough to fit over the air tube on the cat, it fits over the other end no problem however. That is why it's not air tight on both sides.

How exactly does a compression union work? I've googled some pictures to see what it looks like but that wont work with 2 different size diameter pipes will it?
I don't know if it will fit in there anyhow. I only have about a 1" gap between the pipes...maybe 1.5".

Should I try and duct tape it for my emissions test or should I just leave it and hope for the best until I can figure out a better way to join the pipes?