retested today and still failed...everything went down except the NOX levels...this is what i did before todays smog:

stock p28 chip
bigger new cat
ran the car for 30 minutes
plugged in the pcv
connected the vtec oil pressure switch...

what are a couple things that can be causing the NOX level to be high??

 

i have heard if you unplug the pcv it will pass. but i am not sure so dont flame me for it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by yellow rex &raquo;</TD></TR><TR><TD CLASS="quote"> but i am not sure so dont flame me for it.</TD></TR></TABLE>


You ---&gt;

j/k.

 

daym..anyone know if california dmv will allow me to have the smog due extended?? ive aleady had it extended once...will they let me do it again??? still need help...ive heard retarding the timing will lower the nox level...anyone know if this is correct??

 

Retard will definitely help NoX. It'll raise most everything else though.

A little bit of nitrous?

 

here are my numbers:

15mph
co2-14.44
o2-0.00
hc- max-142 meas- 85
co- max- .86 meas-.08
no- max-873 meas- 3410

25mph
co2-14.80
o2-0.00
hc- max- 117 meas- 30
co- max- .76 meas- .03
no- max- 812 meas- 3135

this was my retest..i failed the first time...by alot...at least now its only nox...this is what i did after my first test...i replaced the cat with a new heavy duty one..went to a stock p28 ecu program....finally connected the pcv...wired up the vtec oil pressure regulator...the only mods i have are i/h/e...

the car is 88 dx hatchback with a d16z6 using a conversion harness...i also wanted to know since im using a conversion harness which 02 sensor do i need to get??? do i need the obd1 one or the obd0???

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by aallbbeerrtttttt &raquo;</TD></TR><TR><TD CLASS="quote">wow, from those numbers, my bet is a bad cat...

there's really no way the car is running lean because hydrocarbons are good, carbon dioxide is good, and oxygen is REALLY good, carbon monoxide is low, which is good...so the engine is performing well...anything after that is the cat or muffler, my bet is on the cat

and you use the obd1 4 wire o2 sensor</TD></TR></TABLE>

the cat is brand new i just got it installed saturday...could it be the header or the exhaust??? can it be a bad o2 sensor??? i even ran the car hard for 30 minutes to warm up the cat just like the person said at the shop that i got my cat installed at...

 

stop believing rumors go to a smog tech and ask questions.. Plus if your cars stock. your a legal citizen of california and its a test only you qualify for a cap program.. whats a cap program.?? the state pays up to 500 dollars to have you car fixed. You gotta go to the smog place and ask for the form.. they have it in english and spanish.. Nox could be several different things. plus if you believe some of the stuff that some of these people are saying dissconnect this or do that your going to fail for tampered emissions or disconnected or unpluged emissions. so go to a smog tech.. and find out what you can do..( i work at a shop and see this every day trust me..) ps im in the smog class so i learned all this stuff..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RockinDa_"D" &raquo;</TD></TR><TR><TD CLASS="quote">stop believing rumors go to a smog tech and ask questions.. Plus if your cars stock. your a legal citizen of california and its a test only you qualify for a cap program.. whats a cap program.?? the state pays up to 500 dollars to have you car fixed. You gotta go to the smog place and ask for the form.. they have it in english and spanish.. Nox could be several different things. plus if you believe some of the stuff that some of these people are saying dissconnect this or do that your going to fail for tampered emissions or disconnected or unpluged emissions. so go to a smog tech.. and find out what you can do..( i work at a shop and see this every day trust me..) ps im in the smog class so i learned all this stuff..</TD></TR></TABLE>

 

I could be mistaken but I don't believe a Z6 in an '88 hatch would be considered stock.

 

You and I have the same motor and problem it seems. My numbers were similar. I spent over $500 to get my car through it's last smog because of NOx levels (had to test 5 times to pass). Anyway here's what I did...

1. Searched for "nox" and read everything there was on the subject

2. used pass or don't pay, which helped with everything but NOx

3. Timing and higher octane gas (shell 91). This got me closer, but still about twice the legal limit

4. combustion chamber cleaning was my solution. All of that carbon buildup causes it to run hotter, thus producing more nox.... So I would reccomend you go that route... seafoam if you will. It brought my nox down from 2000+ to just under 800. Passing baby

Good luck and keep me updated. I have a smog coming up in January

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SECURITY &raquo;</TD></TR><TR><TD CLASS="quote">You and I have the same motor and problem it seems. My numbers were similar. I spent over $500 to get my car through it's last smog because of NOx levels (had to test 5 times to pass). Anyway here's what I did...

1. Searched for "nox" and read everything there was on the subject

2. used pass or don't pay, which helped with everything but NOx

3. Timing and higher octane gas (shell 91). This got me closer, but still about twice the legal limit

4. combustion chamber cleaning was my solution. All of that carbon buildup causes it to run hotter, thus producing more nox.... So I would reccomend you go that route... seafoam if you will. It brought my nox down from 2000+ to just under 800. Passing baby

Good luck and keep me updated. I have a smog coming up in January </TD></TR></TABLE>

im gonna try that this weekend...hopefully it will work...

 

Just remember to change your plugs after the sea foam.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SECURITY &raquo;</TD></TR><TR><TD CLASS="quote">

4. combustion chamber cleaning was my solution. All of that carbon buildup causes it to run hotter, thus producing more nox.... So I would reccomend you go that route... seafoam if you will. It brought my nox down from 2000+ to just under 800. Passing baby

</TD></TR></TABLE>

Same thing here. I had high NoX levels with my old SOHC. I suggest getting the cleaner from a Chevy/GM dealership. Part number is 12345104. You might have to do it a few times though..and its about $20 a bottle. It really works though!!
I never tried seafoam and probably never will.

BTW it says you WTB a complete vtec solenoid assmebly for D series. I have one for sale. Pm me if you're interested.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by aallbbeerrtttttt &raquo;</TD></TR><TR><TD CLASS="quote">NOx is due to high combustion temperatures

running lean will cause high NOx
a bad cat will cause high NOx

post your numbers and i'll see if i can help you</TD></TR></TABLE>

You are correct about NOx is due to high combustion temperatures.
Running lean is also correct.
Bad cat does not affect NOx as much as High CO and HC does.

Things you can do to lower combustion temp:
-Use a step colder plug for the smog test.
-Do not run your car for 30 min before the smog test. The reason people say you -want your cat "hot" for the smog is because they had high CO and HC but you have high NOx.
-Retard timing. Run at the lower acceptable range(ie if its 12deg-18deg, then run your timing around 11 or 12)
-Highest octane(no octane booster).

I had similar numbers and doing all this lowered my NOx by a couple of hundred. HOpe this helps

 

here in tucson az i just put a gsr in a 92-95 coupe through by unplugging 2 injectors, retarding timing, and bumb the idle up to about 1200

goodluck

 

Deffanitly retard timing.

I failed horribly my first time with NOx because of my cat which wasnt really a cat....

Fixed that and passes wonderfully.

Also do you have a EGR valve? I dont know what kind of car or engine you have, I know since my engine is JDM my NOx levels were naturally higher due to no EGR.

 

anymore ways to lower NOX levels...

 

You want the engine to be running as cool as possible. Make sure your radiator and coolant are good. Smogging on a cool winter day is is definately an advantage compared to smogging in the dead heat of summer when it comes to nox.

Also you can spray a mist of water into the throttle body to act as a "steam cleaner" for your motor. This will send some carbon out of the tail pipes

This is all stuff that is in the archives of old threads on nox, smog, etc

 

my emissions results were similar to yours.

I retarded the timing until the car would barely run and it passed

 

Here are your answers, I am a smogtech here in CA

First of all, cooler the better, Do the test first thing in the morning!
Retard timing 2 degrees below spec. (You need to be in this range to pass functional test, plus or minus two degrees from spec.)
Seafoam - works great and have used it on alot of cars with no ill effects.
Above 3000ppm's for NOx would normally be Cat. Without a cat my car was up in the 3's too. Also a bigger cat is not always better it can take more time to heat up the cat completely. The front half of it is heated up enough to suck all the O2 out but the back half is not hot enough to do it's job correctly. Remember there are two parts to a cat. The front half is for HC and CO the rear half is for Nox.
your O2 #'s are good.
I would try a stock replacement cat. de-carbonize. Timing, and test in the morning.
Oh yea, Don't unplug anything.

 

Smogman knows whats up.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thesmogman &raquo;</TD></TR><TR><TD CLASS="quote">Here are your answers, I am a smogtech here in CA

First of all, cooler the better, Do the test first thing in the morning!
Retard timing 2 degrees below spec. (You need to be in this range to pass functional test, plus or minus two degrees from spec.)
Seafoam - works great and have used it on alot of cars with no ill effects.
Above 3000ppm's for NOx would normally be Cat. Without a cat my car was up in the 3's too. Also a bigger cat is not always better it can take more time to heat up the cat completely. The front half of it is heated up enough to suck all the O2 out but the back half is not hot enough to do it's job correctly. Remember there are two parts to a cat. The front half is for HC and CO the rear half is for Nox.
your O2 #'s are good.
I would try a stock replacement cat. de-carbonize. Timing, and test in the morning.
Oh yea, Don't unplug anything. </TD></TR></TABLE>


daym i paid 150 for the bigger cat...so should i go to a smaller cat? do i still need to warm up the cat for 30minutes??? daym the weather here has been hot so i have to wait for it to be cold in the morning...

 

Well heres my thread for same problem you had and the steps I took that dropped nox down almost to nothing compared to what it was before....https://honda-tech.com/zerothread?id=1668088

 

Warming up the cat, NO
Just get the car to operating temp. By the time we enter all the required info the cat has cooled off.
You don't have to tell me about the temp. My new record for in the shop is 132deg's while doing a test. And it passed!
Thanks YZ for adding the other thread. And a good job to you for getting her to pass.