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Ezzzzy1
Wed Mar 13th, 2013, 11:31 AM
I had a friend that was going to trade in his 01 Denali and so I bought it for the company and towing etc...

So I took it to get the emissions and it didnt pass :(

They are saying "high NOx readings

Wondering if anyone has been down this path before? I have read a lot about it and things are pointing towards the cats but there is also information saying the cats will throw codes but its because something upstream is really the culprit.

Also, I put an aftermarket intake on it and am wondering if that could have leaned it out too much and if maybe thats the problem.

Interested to hear what anyone has to say

Thanks all!

Grim2.0
Wed Mar 13th, 2013, 11:33 AM
What year is it? Does is have NO2 sensors?

madvlad
Wed Mar 13th, 2013, 11:37 AM
Any check engine light at all?

Ezzzzy1
Wed Mar 13th, 2013, 11:49 AM
2001 Yukon Denali 6.0

No check engine light but there were some stored codes. "Catalyst system efficiency below threshold"

Normally I would jump all over the cats but like I said I have read a lot about the cats throwing codes because of something on the intake side. Like the MAF sensor leaning the system and that causing the NOx and then the cat throwing the codes.

Grim there are O2 sensors but no codes (faults)

I heard rumor that if you take the car in while the cats are hot sometimes it will pass because they are essentially burning the results? Anyone?

madvlad
Wed Mar 13th, 2013, 11:55 AM
Could be an intake manifold gasket faulty causing a vacuum leak as well

bulldog
Wed Mar 13th, 2013, 12:06 PM
Any mods?

My car won't pass emmisions with my headers installed! We live in one of the toughest cities for emmisions....f*ck all their lame rules!

I have passed with a intake though, so that shouldn't be a problem

I've always had to replace 02 sensors to pass, but you usually get a code come up if it is one of those

rybo
Wed Mar 13th, 2013, 12:07 PM
Having the engine warm helps a lot

Running GOOD fuel helps a lot

running a fuel system cleaner like Seafoam can help

Cleaning the MAF can help

Making sure that you have a good gas cap can help

Giving it an "italian tune up" (flog it down the interstate a bit) can help

bulldog
Wed Mar 13th, 2013, 12:17 PM
Having the engine warm helps a lot

Running GOOD fuel helps a lot

running a fuel system cleaner like Seafoam can help

Cleaning the MAF can help

Making sure that you have a good gas cap can help

Giving it an "italian tune up" (flog it down the interstate a bit) can help +1

Most auto parts stores sell special formula to help pass emmisons too.

Usually when they fail you they give you a sheet explaining what failed and what needs to be fixed. Did he not get this?

Grim2.0
Wed Mar 13th, 2013, 12:20 PM
+1

Most auto parts stores sell special formula to help pass emmisons too.

Usually when they fail you they give you a sheet explaining what failed and what needs to be fixed. Did he not get this?


"high NOx readings

They wont give you a solution for this though.

madvlad
Wed Mar 13th, 2013, 12:27 PM
2001 Yukon Denali 6.0

No check engine light but there were some stored codes. "Catalyst system efficiency below threshold"

Normally I would jump all over the cats but like I said I have read a lot about the cats throwing codes because of something on the intake side. Like the MAF sensor leaning the system and that causing the NOx and then the cat throwing the codes.

Grim there are O2 sensors but no codes (faults)

I heard rumor that if you take the car in while the cats are hot sometimes it will pass because they are essentially burning the results? Anyone?

Shoot me through PM what the stored codes are and I'll see how I can help you out man

bulldog
Wed Mar 13th, 2013, 12:36 PM
"high NOx readings

They wont give you a solution for this though. Doesn't that mean cats are not doing their job then? Maybe a blown out cat as I have heard of that happening; cat is there, but stuff inside is toast

Ezzzzy1
Wed Mar 13th, 2013, 12:49 PM
Having the engine warm helps a lot

Running GOOD fuel helps a lot

running a fuel system cleaner like Seafoam can help

Cleaning the MAF can help

Making sure that you have a good gas cap can help

Giving it an "italian tune up" (flog it down the interstate a bit) can help

Im going to clean the MAF and get a new cap (even though it passed the test).

Thanks for the info!

Ezzzzy1
Wed Mar 13th, 2013, 12:50 PM
Shoot me through PM what the stored codes are and I'll see how I can help you out man

Done! Thanks buddy!

Ezzzzy1
Wed Mar 13th, 2013, 12:52 PM
Doesn't that mean cats are not doing their job then? Maybe a blown out cat as I have heard of that happening; cat is there, but stuff inside is toast

It could mean that but thats where it gets confusing.

So no one really thinks the intake could make a difference? Stock vs aftermarket

Grim2.0
Wed Mar 13th, 2013, 12:56 PM
It could mean that but thats where it gets confusing.

So no one really thinks the intake could make a difference? Stock vs aftermarket

It could if its sucking in more air and it wasnt "tuned" it could be dumping too much gas in.

I'm surprised the O2 sensors haven't thrown a code, it is possible though that they are both shot and just not doing anything. I cant tell you how many times i had to replace the O2 sensors in my jeep, and i had a after market intake.

bulldog
Wed Mar 13th, 2013, 12:57 PM
It could mean that but thats where it gets confusing.

So no one really thinks the intake could make a difference? Stock vs aftermarket I have passed with a AEM Cold Air and I short Ram before.

I've always heard on my car clubs if too much NOx you need a new (or better) cat :dunno:

rybo
Wed Mar 13th, 2013, 01:00 PM
It could mean that but thats where it gets confusing.

So no one really thinks the intake could make a difference? Stock vs aftermarket

Intake is more of a "demand" than a supply system. The engine draws the amount of air it needs. If you were adding forced induction of some type I could get behind it being a problem, but the ECU in the car should be able to adjust mixture to cope with any range of intake options, even up to removing it entirely. I'm not thinking it's the culprit.

The other system to consider is the EGR system - if there is a problem there it could cause high NOX, but I would suspect there would be a code in the ECU if that was a problem.

NOX is a result of high cylinder / combustion temperatures. There are a couple of ways that this can happen, and it is the primary reason we've seen the demise of high compression / high performance engines. So, a high compression ratio makes more NOX than a low compression ratio. You can get additional compression by there being a bunch of gunk in the engine taking up valuable cylinder space. Engine overheating can cause it because cylinder temperatures get too high. Too much exhaust gas from EGR can cause it because that air is "pre-heated" -

I would start with good fuel, and some cleaning and a nice drive with some "IT tune up" and take it back. If your number was just a LITTLE outside of the acceptable range then this might clear it up. If it was a lot, then you have to diagnose further, but the most likely cause is a dead catalytic converter.

Ezzzzy1
Wed Mar 13th, 2013, 01:05 PM
Intake is more of a "demand" than a supply system. The engine draws the amount of air it needs. If you were adding forced induction of some type I could get behind it being a problem, but the ECU in the car should be able to adjust mixture to cope with any range of intake options, even up to removing it entirely. I'm not thinking it's the culprit.

The other system to consider is the EGR system - if there is a problem there it could cause high NOX, but I would suspect there would be a code in the ECU if that was a problem.

NOX is a result of high cylinder / combustion temperatures. There are a couple of ways that this can happen, and it is the primary reason we've seen the demise of high compression / high performance engines. So, a high compression ratio makes more NOX than a low compression ratio. You can get additional compression by there being a bunch of gunk in the engine taking up valuable cylinder space. Engine overheating can cause it because cylinder temperatures get too high. Too much exhaust gas from EGR can cause it because that air is "pre-heated" -

I would start with good fuel, and some cleaning and a nice drive with some "IT tune up" and take it back. If your number was just a LITTLE outside of the acceptable range then this might clear it up. If it was a lot, then you have to diagnose further, but the most likely cause is a dead catalytic converter.

Im with ya and agree. My worry was that the intake could have "leaned" the system but I think you are right, the ECU would have corrected the A/F ratio. Maybe I will re-set the ECU and make sure that its able to get a good base reading.

It was about 7% off (or failed by that much) so I am guessing the handful of things you suggested will work :fingerscrossed:

jcj81
Wed Mar 13th, 2013, 01:07 PM
if it had a code set in history for Catalyst System Efficiency (P0420,p0430 bank1 and 2) its about 99% chance its faulty converters, if its running lean it will set lean codes P0171,p0174 intake gaskets are common, egr sticking open can cause high nox but egr would set a code for performance if sticking yearly model years had egrs. Mass air flow sensor possible not likely, with out seeing data for fuel trim to make sure its all good I'd go with converters.

jcj81
Wed Mar 13th, 2013, 01:13 PM
[It was about 7% off (or failed by that much) so I am guessing the handful of things you suggested will work :fingerscrossed:[/QUOTE]

since its just barely out you could have carbon build up just enough to raise temps, do a decarbon let it soak. Older years with higher miles have had slight carbon issues usually will notice slight ping on accel engine at operating temp

Ezzzzy1
Wed Mar 13th, 2013, 01:14 PM
if it had a code set in history for Catalyst System Efficiency (P0420,p0430 bank1 and 2) its about 99% chance its faulty converters, if its running lean it will set lean codes P0171,p0174 intake gaskets are common, egr sticking open can cause high nox but egr would set a code for performance if sticking yearly model years had egrs. Mass air flow sensor possible not likely, with out seeing data for fuel trim to make sure its all good I'd go with converters.


If you have a minute I will post up the data

Ezzzzy1
Wed Mar 13th, 2013, 01:22 PM
http://i125.photobucket.com/albums/p55/Ezzzzy1/photo13-1_zps8ab8e596.jpg

http://i125.photobucket.com/albums/p55/Ezzzzy1/photo23-1_zpsf4173cdb.jpg

jcj81
Wed Mar 13th, 2013, 01:23 PM
So it said check engine light on with both p0420,p0430, you have converters failing. About 100% of the time that ive had those codes its been converter on those trucks

Your short term fuel is normal to slight rich
Your long term is way lean

I think you have bad converters but something is causing them to go bad.

Id say leaking intake gaskets and or skewed MAF sensor. Skewed MAF is hard to see a failure
lekaing intake gaskets if you spray carb or brake clean aerosol around intake you could feel a change in idle if they area leaking or some other vacuum leak

birchyboy
Wed Mar 13th, 2013, 01:44 PM
How good is the friend? Depending on the county, the seller is required to provide an emissions test.

Ezzzzy1
Wed Mar 13th, 2013, 01:56 PM
So it said check engine light on with both p0420,p0430, you have converters failing. About 100% of the time that ive had those codes its been converter on those trucks

Your short term fuel is normal to slight rich
Your long term is way lean

I think you have bad converters but something is causing them to go bad.

Id say leaking intake gaskets and or skewed MAF sensor. Skewed MAF is hard to see a failure
lekaing intake gaskets if you spray carb or brake clean aerosol around intake you could feel a change in idle if they area leaking or some other vacuum leak

Som bitch! What do you think the chances of me doing a slight tune up and taking it back hot as hell and it passing? It only failed by a little, right?

I appreciate you taking a minute to look at that stuff

Ezzzzy1
Wed Mar 13th, 2013, 01:58 PM
How good is the friend? Depending on the county, the seller is required to provide an emissions test.

Hes a good friend.... Stuff like this just sucks.

Its actually a Colorado law (the Lemon law) and you are right its on the seller. They technically are not allowed to sell a car that cant pass.

So does that mean he is responsible for fixing it? Im not sure what I am going to do or if I am even going to tell him but im just curious. I just want to get it to pass....

birchyboy
Wed Mar 13th, 2013, 02:03 PM
I think he technically is on the hook for whatever the truck needs to pass. Depending on how much it costs, though, is losing the friendship worth it? Tough spot for you to be in. Good luck!

jcj81
Wed Mar 13th, 2013, 02:10 PM
Som bitch! What do you think the chances of me doing a slight tune up and taking it back hot as hell and it passing? It only failed by a little, right?

I appreciate you taking a minute to look at that stuff

Im not sure, not much you can really tune besides plugs and wires pcv,and I dont really think that is going to cure it, get the codes cleared, decarbon top end, make sure it has acdelco plugs (GM 12621258,acdelco 41-110) they dont do well with other brand pulgs, get it hot and retest but make sure you get the codes cleared, even if the check engine lights not on if its stored in ECM/PCM history they will fail it.

Ezzzzy1
Wed Mar 13th, 2013, 02:46 PM
Im not sure, not much you can really tune besides plugs and wires pcv,and I dont really think that is going to cure it, get the codes cleared, decarbon top end, make sure it has acdelco plugs (GM 12621258,acdelco 41-110) they dont do well with other brand pulgs, get it hot and retest but make sure you get the codes cleared, even if the check engine lights not on if its stored in ECM/PCM history they will fail it.

Well hell...

I think I just my buck the system and do the wires and plugs and even maybe the cap. Clean the MAF sensor and I want to check the timing even though its got to be close.

Whats the best way for someone to get the codes cleared?

Grim2.0
Wed Mar 13th, 2013, 02:48 PM
Well hell...

I think I just my buck the system and do the wires and plugs and even maybe the cap. Clean the MAF sensor and I want to check the timing even though its got to be close.

Whats the best way for someone to get the codes cleared?


That other guy who knows everything about cars and blows my mind prob has a better answer, but i know you can get them cleared at AUtozone.

jcj81
Wed Mar 13th, 2013, 03:01 PM
Well hell...

I think I just my buck the system and do the wires and plugs and even maybe the cap. Clean the MAF sensor and I want to check the timing even though its got to be close.

Whats the best way for someone to get the codes cleared?

This system is coil over meaning each cylinder has its own coil no distributor no cap/rotor no way to check or adjust timing all computer set and controlled, for clearing sometimes removing both battery cables from battery holding positive and negative together for about 30 sec will clear(MAKE SURE YOU DO NOT HAVE A DUAL BATTERY SET UP IF YOU DO IT THIS WAY!) this will discharge reset modules, if not see if a parts store will clear them thats the best way and you can make sure all history codes are for sure cleared.

Ezzzzy1
Wed Mar 13th, 2013, 03:05 PM
Nice. I have a lot to learn when it comes to the American car world.

Good to know that the timing is set because a lot of people were saying that timing thats to advanced can cause NOx fail.

I really appreciate your time man

jcj81
Wed Mar 13th, 2013, 03:26 PM
yeah no problem

madvlad
Wed Mar 13th, 2013, 03:49 PM
I can let you borrow my generic code reader to clear them shits out

sag
Wed Mar 13th, 2013, 07:09 PM
mix some ethanol in there

Ezzzzy1
Wed Mar 13th, 2013, 07:32 PM
mix some ethanol in there

I actually heard that... Any experience with doing that?

I went down to the Auto Parts joint down the road and he let me use their reader. It was just the two cat codes and I cleared them out. The guy swore by this stuff call "guaranteed to pass", they say if you dont pass using it that they give you double your money back. I put it in and need to burn the whole tank of gas and then fill up with premium. Should be good to go but I will let yall know how it goes.

Damir, thanks for the offer man. I will let you know.

spideyrdr
Wed Mar 13th, 2013, 08:01 PM
RE: A code reader: I can endorse this reader which can be used to clear codes:

http://www.amazon.com/Autel-MaxiScan-MS300-Diagnostic-Vehicles/dp/B001LHVOVK/ref=sr_1_1?ie=UTF8&qid=1363226243&sr=8-1&keywords=engine+code+reader

It's $20, it's simple, it does the job. It's not pro-grade but for simple diagnostics and clearing of codes, it's sufficient for a shade tree mechanic.

Ezzzzy1
Wed Mar 13th, 2013, 08:15 PM
RE: A code reader: I can endorse this reader which can be used to clear codes:

http://www.amazon.com/Autel-MaxiScan-MS300-Diagnostic-Vehicles/dp/B001LHVOVK/ref=sr_1_1?ie=UTF8&qid=1363226243&sr=8-1&keywords=engine+code+reader

It's $20, it's simple, it does the job. It's not pro-grade but for simple diagnostics and clearing of codes, it's sufficient for a shade tree mechanic.

I now have one headed my way. This will come in handy from time to time.

Thanks a bunch!

jcj81
Wed Mar 13th, 2013, 08:53 PM
If you add E85(Ethanol) fuel to a vehicle not made to run E85 it wont help it run better while it has a high ignition point think higher octane, it takes more fuel to make the same energy as regular fuel, so e85 vehicles flow more fuel to make the power and ecm/pcm software(timing,injector pulse,ect) to run properly, adding E85 to a vehicle that wasnt made for it doesnt add fuel properly so it ends up running lean which your truck is already lean so dont think it will help with your concern.

spideyrdr
Wed Mar 13th, 2013, 08:56 PM
I now have one headed my way. This will come in handy from time to time.

Thanks a bunch!


You bet! I hope it works for you. I have used mine to pull codes on my Jeeps and reset my wife's codes (O2 sensor) and pass emissions. My neighbor used it to troubleshoot his issues on his truck. I liked it so much I got one for my dad for xmas.

Jamie

sag
Wed Mar 13th, 2013, 09:06 PM
we did it at the shop to pass a few primarily race cars. the alcohol evaporating takes soooo much heat out of the charge. wouldnt put more than a few gallons in a full tank. then drive it around staying closed loop so it can mix. but yep, e85 needs about 33% more fueling to have the same energy potential of gasoline so dont go hotrodding with e85 in the tank.

#1Townie
Wed Mar 13th, 2013, 09:16 PM
http://www.smogtips.com/failed-high-NO-nitrous-oxide.cfm

But hey really if just use a friends address in another county that doesnt have emissions you dint have to worry about it.

highpsi03
Wed Mar 13th, 2013, 09:26 PM
The guarenteed to pass stuff is basically alcohol. If you have failing you can pass a few different ways:

Run the car down to almost empty, fill up with some 85 octane (yes 85 octane) The lower octane burns faster. Add a few bottles of rubbing alcohol and go back and re-test. It'll pass. If not....

Loosen the exhaust somewhere. Wether it be the downpipe or after the cat. Don't get to crazy, just enough so that some exhaust comes out. Less exhast in the back means the machine reads less. Better chance of passing.

teamextreme
Wed Mar 13th, 2013, 09:48 PM
Loosen the exhaust somewhere. Wether it be the downpipe or after the cat. Don't get to crazy, just enough so that some exhaust comes out. Less exhast in the back means the machine reads less. Better chance of passing.

I'm pretty sure this will have no effect. By creating an exhaust leak you've changed the volume of exhaust getting to the sensor, but you haven't changed the composition of the gases that are still getting there, which is what the sensors are reading. And by creating an exhaust leak, I'm not positive, but pretty sure you've introduced another reason they can fail you if they notice it.

Ezzzzy1
Wed Mar 13th, 2013, 10:50 PM
http://www.smogtips.com/failed-high-NO-nitrous-oxide.cfm

But hey really if just use a friends address in another county that doesnt have emissions you dint have to worry about it.

That's some good info. Thanks man.

Funny thing is that I called the old man tonight and asked "if I can't get this emmisions thing figured out, can I register it out there?" :lol: Plan B :)

highpsi03
Thu Mar 14th, 2013, 07:19 PM
I'm pretty sure this will have no effect. By creating an exhaust leak you've changed the volume of exhaust getting to the sensor, but you haven't changed the composition of the gases that are still getting there, which is what the sensors are reading. And by creating an exhaust leak, I'm not positive, but pretty sure you've introduced another reason they can fail you if they notice it.
It will work. When i had my old eclipse i did it every time emissions came around and it passed every time.

BadR6Man
Thu Mar 14th, 2013, 11:01 PM
High Nitrogens of oxide is simply your egr system not working properly. I woukd suggest since your readings are slightly over the limit that your egr ports are restricted. Remove egr valve and clean thouroughly with solvent. Should pass afterwards.

The cat codes are a totally different problem. Your SES lamp should be on for those codes. Most 420 and 430 codes will require replacement of cats.
Im not sure if they are using the IM240 test here in CO. After clearing the codes, the vehicle still needs to go through a drive cycle or you will fail again.

Ezzzzy1
Thu Mar 14th, 2013, 11:05 PM
High Nitrogens of oxide is simply your egr system not working properly. I woukd suggest since your readings are slightly over the limit that your egr ports are restricted. Remove egr valve and clean thouroughly with solvent. Should pass afterwards.

The cat codes are a totally different problem. Your SES lamp should be on for those codes. Most 420 and 430 codes will require replacement of cats.
Im not sure if they are using the IM240 test here in CO. After clearing the codes, the vehicle still needs to go through a drive cycle or you will fail again.

Sounds like you know your shit! I appreciate it.

Question, what is your definition of drive cycle?

I was driving it today to try and burn up the tank of gas that has the "guaranteed to pass" stuff and the check engine light popped on again. Id say it stayed off for about 10 miles...

bulldog
Fri Mar 15th, 2013, 08:03 AM
Check engine lights are a immediate fail right?

I even tried getting it cleared before I went and they caught me still on that code :lol:

Ezzzzy1
Wed Mar 20th, 2013, 05:40 PM
FUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUCK!


Yeah, so beast failed again and even worse. Went from failing 2150 or whatever to 2300 something. The limit of NOx is 2000

What I did:

Used "guaranteed to pass" (I call bullshit :lol:)
Burned a whole tank of gas with that in
Literally pulled up to the gas station on an empty tank and filled halfway up with 91
Went and had the check engine lights reset
Drove from Castle Rock to Monument and back then pulled straight into the emissions place. I didnt have to wait, was the first car there.

WTF?

Anyone get the hookup on GM parts? I think I need to just replace the cats :(

Open to other options, might even try the ethanol method. :nuke:

jcj81
Wed Mar 20th, 2013, 05:48 PM
I can get you GM parts prices in the morning.

Ezzzzy1
Wed Mar 20th, 2013, 06:32 PM
I can get you GM parts prices in the morning.

I would appreciate that!

Its just looking like the cats but im not that well versed in GM...

Maybe O2 sensors too?

koop
Sun Mar 24th, 2013, 01:07 PM
Before you drop bucks on cats, try seafoaming it. My truck failed and Seafoam made it pass with flying colors.

http://ls1tech.com/forums/general-maintenance-repairs/534376-how-seafoam-your-car.html