Hey techers!
Like every honda i failed nox. my co,and hc readings are below specs.the nox is 1632 at 15mph, and 2407 at 25 mph.This is on a 95 gsr skunk2 mani, 2 1/4 exhaust,injen cold air intake, msd ignition.hi flow cat. 14deg btdc.
Possible culprits are:
Msd ignition= hot spark or gap issue
Cold cat=not warmed up correctly
valve lash= .007 intake .009 exhaust i think......
bad fan switch= fans hardley ever comes on but the smog tech said my water temp was low. Anyone have any leads i can start at? The head was tooken off and rebuilt,clean with itr valves and sprins ti retainers, bronze valve guides. i cleaned the pistons too. so there shouldent be to much carbon. thanks.

 

Bump I searched every topic related to nox and i still know more than them.

 

Also the big trade off with denautured alcohol While im at it is a colder mist in cc,but might affect hcs and a hotter burn.also i heard alcohol is much thinner than gas so you might just run too rich. I tried alcohol at my last smog and my nox was high at 15mph 2227, then at 25mph it went to 114. things really got cold there but i almost failed hcs. ?

 

A lil help here!!!!!!!

 

bump

 

When I failed the sniffer, it was because of a bad cat and o2 sensor. After replacing them, I passed with flying colors... but my motor is basically stock.

From what I've read, it's a good idea to run your car hard right before it goes to the sniffer. There is something at the parts store too that supposedly helps you pass emissions.

good luck... I hate emissions testing.

 

how you doin bro ?i'm chris a mechanic from australia i got done for emissions aswell . the things you need to do are 1 replace hiflow cat back to standard cat 2 put ignition timing to 9-10 degrees 3 use the lowest octane fuel available e.g 91 octane 4 use a hot plug to burn the fuel 5 most important make sure you have no exhaust leaks. good luck bro.

 

thank you for the reply guys.heres what im thinking
cali will only allow you to change timing +or- 2 degrees from the factory set timing. so i cant do any of that. Im going to run an intrusive on the exhaust manifold and that will tell me if my cat is performing or if it really is my engine. Do you thikn since itr valves have less of a dish my compresion could be affecting nox im sure its not even that much a compression change but you never know.....

 

bump
ttt

 

Did you do the basics before the test?

Change plugs, wires, cap, rotor......a thorough sea foam cleaning.....then before the test bring it to redline in 1st, 2nd so that the cat is hot and so that it might burn some carbon off of the o2 sensor.

Or...do you have a chipped obd-1 ecu? Drop in a tune that's really lean

 

yeah i did the basics, i think its just my cat not heating up properly. Honda put out a tsb for failed emmsions. the corrective action was to drive aggressive for 25 miles then smog it. then they wised up and put the cat upstream toward the head. Anymore ideas? here are the readings...
15mph hcs 73, co 0.03, nox 1632, co2 14.60, o2 0.49
25mph hcs 69, co 0.02, nox 2407, co2 14.30, o2 0.76
thank you!

 

Don't forget the oxygen sensor. A bad oxygen sensor can cause NOx to be high.

 

thanks you guys, the o2 sensor was changed, my numbers arent to bad. im sure my valve lash could be looked at a lil closer. also i read that someone said if you have a leaky brake booster it can cause nox to sky rocket? that sounded good to me. my brake pedal goes gradually to the floor when applied. thank you

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93hatchin &raquo;</TD></TR><TR><TD CLASS="quote"> thanks you guys, the o2 sensor was changed, my numbers arent to bad. im sure my valve lash could be looked at a lil closer. also i read that someone said if you have a leaky brake booster it can cause nox to sky rocket? that sounded good to me. my brake pedal goes gradually to the floor when applied. thank you </TD></TR></TABLE>

8 times outa 10 it's the cat on your car... I've seen many cars that need to replace a cat because of NOX, if the o2, compression, tune-up, etc... is good then it's down to the cat because there's no egr.

NOX reduction is the first thing that fails in a cat. converter.

 

nice Im almost sure its the cat could my 2 1/4 piping be a possible culprit also? I highley doubt I have something in my cylinders getting over 2500 degrees.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xsflow &raquo;</TD></TR><TR><TD CLASS="quote"> put ignition timing to 9-10 degrees 3 use the lowest octane fuel available e.g 91 octane 4 use a hot plug to burn the fuel </TD></TR></TABLE>

Bad advice. I would retard the igniton timing lie he said but, 99% of the time a high NOx reading can be cured by using higher octane fuel. High NOx is caused by combustion chamber temps being too high. If you richen up the mixture it may bring the HC's up so that is not a good option either. Retard the timing and use a higher octane fuel even if it has to be a "race" gas (98 octane+). Good luck.

Phil

 

im not understanding the whole high octane vs low octane thing.lets think it out. high octane stands up to higher temps and pressure.applications for high octane are high cylinder pressures,and compressions.Maybe also to prolong the carbon deposit predetonation issues.anything else?

 

retard your ign timing all the way and het "guaranteed to pass" from napa or the like. works great.

 

my timing is all the way retarded, im working on running seafoam today im concerned if there is anything mechanical going on that is causing this.tia

 

use "GTP" like i said.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hybridvteceg &raquo;</TD></TR><TR><TD CLASS="quote">retard your ign timing all the way and het "guaranteed to pass" from napa or the like. works great. </TD></TR></TABLE>

In cali, you can't retard or advance your timing more than 3 degrees from specs.... Also, I've seen many people use the guarantee to pass stuff.... it doesn't work if you're failing emissions by alot... it might help if it was borderline.

 

i was failing by a lot and those two tricks passes me, raised CO though

 

look at these numbers!!!!! they are so good, besides the nox
15mph hcs 73, co 0.03, nox 1632, co2 14.60, o2 0.49
25mph hcs 69, co 0.02, nox 2407, co2 14.30, o2 0.76
my 02 looks high compared to all my other previous test. if im correct the 02 should be low meaning the cat is using up all the 02. my cat aint functioning properly what you guys think?

 

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

In cali, you can't retard or advance your timing more than 3 degrees from specs.... Also, I've seen many people use the guarantee to pass stuff.... it doesn't work if you're failing emissions by alot... it might help if it was borderline.</TD></TR></TABLE>

Retarding the timing 3 degrees and using higher octane fuel will help substantially. 93Hatchin, Have you done either of these? NOx is a product of high combustion chamber temps and you must do something to bring them down. Trust me

Phil

 

i have, my timing is 14 deg btdc i currently have 89 octane in there..... tommorrow im getting an intrusive so i can cut my problems in half. if it isnt my cat then i will be doing a valve adjustment, along with some other goodies. if it is my cat i will be swapping it out for a better one.ty