Thread: smog. help me diagnose a barely fail in the NO category

My friend passed his last test about 2 years ago, and has pretty much all the same stuff except a greddy header. He has a 2gnt also.
i went and tested today. i passed every category, except for NO at 15 mph, passed in the 25 mph though.

hc at 15mph was just under the max allowed too, but passed. co was awesome. and hc at 25 was good too.

im thinking because the aftermarket header has the o2 sensor moved, that it might be that negative effect on my NO.

Im not sure what else it could be. Any ideas?

And if it is the header, im hoping either i or he still has his stock one and i'll switch back to it. Do you guys have any no reducing tricks for smog so we can avoid doing that work though?

Thanks

actual numbers for everything:



CO2 at 15mph = 14.7, 25mph = 14.6; O2 at 15 = .2, at 25 = .1; HC at 15= 52, 25 = 17; CO at 15 = .23, at 25 = .07; NO at 15 = 552, at 25 = 265

maximums are(starting with HC): HC at 15 = 52, at 25 = 36; CO at 15 = .49, at 25 = .46; NO at 15 = 424, at 25 = 711


Thanks for any help you can provide. I was thinking about mixing ethanol or other fuel treatment/emission reducer during my next test to see if its enough to pass. thoughts?

Originally Posted by george536

I honestly believe your cat wasn't hot enough, your air fuel mixture by looking at you CO2 is about right. Your nox and co declined by a lot when you got to 25. Meaning your cat finnally fired up and did its job. If it was mechanical or a lean misfire nox would of increased. I would honestly test it again and sit in your car reving at like 2k keeping it hot untill you hand over the keys. also this might sound weird but max out your tires on psi. Easier turn on the dyno less load on the motor. We had a honda in my smog class and it would keep failing nox and I couldn't f@c< figure it, and my teacher would laugh at me, untill he told to check the tire pressure and it was at like 10 psi. Air them up and passed. Less load on the motor, less heat in cylinders, less nox.

where are you going to school?

I'm over at UTI. I havent gone thru the diagnostics class yet, but from what i've learned in my ignition and fuel class, usually NOx can be caused by a lean problem, and HC's show catalytic converter effiency, so thats why i havent been to sure about how to address the problem. i know his cat is fine, and my O2 sensors are good - tested them 2 months ago. we put in an emission reducing fuel additive to try and clean up some carbon buildup to see if it will be enough. as you can see he's not too far off from passing...only like 130 parts per million. but we'll definitely keep the car running. I've heard that having to start the car a couple times before the test can be enough to fail. my tires aren't maxed out but they're only 5 psi under max.

someone suggested that i put "Heet" in his fuel tank right before the test because it will make the engine run a little hotter. Heet is meant to remove water from fuel, so it either has alcoholic properties or just plain contains alcohol. What do you think?

Someone else said i should put a 50/50 mix of my normal gas and methanol fuel - but i dont even wanna try that because i know thats bad for fuel lines and fittings. not to mention the only place i know you can get it is at Tognotti's, and only comes in a 5 gallon bucket for like $35.

Originally Posted by george536

I honestly believe your cat wasn't hot enough, your air fuel mixture by looking at you CO2 is about right. Your nox and co declined by a lot when you got to 25. Meaning your cat finnally fired up and did its job. If it was mechanical or a lean misfire nox would of increased. I would honestly test it again and sit in your car reving at like 2k keeping it hot untill you hand over the keys. also this might sound weird but max out your tires on psi. Easier turn on the dyno less load on the motor. We had a honda in my smog class and it would keep failing nox and I couldn't f@c< figure it, and my teacher would laugh at me, untill he told to check the tire pressure and it was at like 10 psi. Air them up and passed. Less load on the motor, less heat in cylinders, less nox.

HEAT the cat up well before you test again.. just like george said.. You can ask the smog tech to condition the cat as well and he will run it through a cycle on the smog machine designed to heat the cat up.

If you still fail.. replace it..

Dont bother with figuring out additives and crap.. You will probaby end up making your numbers worse.

yup you were right. turned it just needed to be warmed up more. he passed. or it could've been cuz he just didnt turn it off. i remember it having to be started like 3 times last time.

i'm getting mine smogged like tomorrow. i should pass no problem.

my car passed first try today. :P 8)