I have a stock B18 in a 93. Only mod is intake. HC and CO were barely passing. NOX was way high:

15mph - Max could be 750ppm. It was reading 1900ppm.
25mph - Max could be 750ppm. It was reading 1200ppm.

Any ideas or suggestions? My neighbor who is a long time mechanic said that it could be due to my advanced timing. I had it set at 18 deg during the test. I retarded it just now to 14 deg. He mentioned a failed EGR system. But I believe there is no EGR in the 93 Integra. He also mentioned hot combustion chambers and running lean. I did change the spark plugs and changed the oil and noticed that the plugs read a little bit lean. That could of been from the advanced timing which I have fixed. I also asked my mechanic about replacing the cat but he mentioned that it wouldn't do much if anything at all in regards to the NOX levels. It will help decrease the HC and CO levels but nothing to the NOX. The guy at the smog test station said that backing off the timing will help but not enough to pass. Anybody have any ideas or suggestions? I open to anything and need to get this thing registered next week. Appreciate any help. Thanks.

-Leo

 

change out you cat

 

Possibly your O2 sensor? if 93 had one that had anything to do with nox

 

i'm a smog tech myself.. it could be that you have carbon build up in your engine.. might need to clean it out, may even have to pull off the head to crave it out... make sure that your O2 switch time is good and that all your sensor are working properly... the cat will not help much at all for NOX.. only for hc and co

 

The stock cats are three way catalysts. Aside from oxidizing HC's and carbon monoxide to carbon dioxide, they also reduce nitrogenous oxides to free nitrogen (N2).

It's in the service manual.

I'm putting my bets on the cat b/c you're barely passing on the first two and failing the NOx test, but I'd still check other culprits too.

O2 sensor, cooling system, plug heat range, carbon build-up, etc.

 

Appreciate the replies. I've read quite a few threads regarding the high NOX levels. Some say change the cat, some say it will hardly affect NOX, only help HC and CO levels. I don't want to go out and spend $200 parts and labor for the cat and still fail.

How do I check if the O2 is working properly? I'm pretty sure it is since I have no CEL. I know that the motor is running lean though since I read the plugs last week and they were pretty white. I attributed that to the advanced timing set at 18-19 deg. But I backed it out to 14 deg now.

Some say use high octane or octane booster or some sort of fuel injector cleaner, but some say use the lower octane because it'll burn more completely easier. In my particular case, I would guess that the high octane would be better since I may still be running lean. Haven't checked the plugs yet since I backed the timing down. Any thoughts on this?

Since NOX is produced when the combustion chambers reach 2500 deg and above, I'm trying to figure out a few ways to cool it down. My cooling system seems to be working okay. High octane if it's running lean, retarded the timing, what else? I've heard of using GM's Top End Cleaner to clean out any carbon deposits in the head which may attribute to higher compression and hence higher cc temps.

Can anyone explain the denatured alcohol and how that may help?

Thanks again for the help and replies. I need to get this done so I can register my car by the end of this month. Appreciate it very much.

 

there was a discussion on seafoam and how it helps to reduce carbon inside ur engine. or try using auto-rx that i've read on bobistheoilguy.com site.

 

there are two types of O2 sensors, Zirconium and titania ( I dont know what hondas use).......basically they will tell your computer to run rich or lean depending on the gasses they sense......to test for them you kinda need an Osciliscope, and backprobe the connector NOT THE WIRES going into the sensor you will kill it. Set the Scope to O2 and look what type of signal it produces, if its a flat line then your O2 sensor is bad.

 

I had the same problem with the high nox level. My mechanic did a full diagnostic of the smog related components and found nothing wrong. Changed the cat and it passed with flying colors. Mechanic thought there was buildup of crap in the engine because it burns a little bit of oil and has 200k miles......

 

nox is created when combustion occur, the hotter the combustion the higher the nox, there are few ways to reduce nox, one is by ising 100octane, (don't use otane boost, they help reduce pre-ingintion but most does not lower combustion temp.)
you could get a new cat then richen the mixture (running rich lowers combustion temp, but you need a new cat to clean up the hc and co created by running rich)
at worst remove the head and run a thicker head gasket to lower comp. ratio.

but for now try running a colder plugs,retard timming and 100 octane gas.
also try to smog early in the morning whe its still cold outside


Modified by esponet at 8:00 PM 3/10/2004


Modified by esponet at 8:01 PM 3/10/2004

 

I was the same way i had really high nox everything else was fine. i changed the CAT and it droped from 1800 to 200. Anyone that says cat dont affect nox bullsh*t. I have seen it with my own eyes. i only payed 100.00 installed. This was on my stock 92 ls.

 

Ahh...considering changing the cat now. I'm going to change the thermostat tonight, already retarded the timing, colder plugs (i'm running stock ngks heat range 5 now) and try and find some 100 octane.

integlikewhoa: Did you ask for the 3-way catalyst when you purchased the cat?

Any other ideas suggestions?

 

100 octane, good luck, you're gonna have to go to a track like sears point to get some.

try and adjust your valves while your at it too.

also you can pay your registration fee even if you don't have your smog yet. they just won't issue your new reg tags till the smog is transmitted to the dmv. i did that last year to avoid the late fees.

 

These were my results:

15mph
HC Max is 89 ppm. Measured at 87.
CO Max is 0.53 ppm. Measured at 0.64.
NO Max is 708 ppm. Measured at 1937.

25mph
HC Max is 54 ppm. Measured at 56.
CO Max is 0.51 ppm. Measured at 0.46.
NO Max is 746 ppm. Measured at 1231.

After taking to my neighbor who is a mechanic and other threads here saying a new cat won't help NOX at all, I'm not sure. But if I have to change it out, I have no other choice.

Any other places besides Sears to find some high octane preferably here in the Berkeley east bay area?

 

sac speedway. damn hippies in CA won't let us have the really good octanes.

 

looking at the result, i would recomend you change the cat also, as you are on the border on your hc and co,

100 octane can be purchase around bay area, i know there was a gas station in sj tha used to sell them on the pumps, 76 station,

 

I have bene asking about this for about 3 weeks, no one seems to know what to do but your post many people opened up, so please let me knwo what you do, I am about to swap my engine, cause its got 200K and this dam high NOx crap. but if a cat and some 100 oct will do I would be much happier.

Thanks all

 

erc racing fuel, in san leandro or san lorenzo
or contact dnr in hayward i'm sure he can get you 100 octane but make sure its unleaded

 

PASSSSSSSSSSSSSED!

I can sleep good for another 2 years. Results and timeline below:

Tuesday: Tested and failed.

Thursday:

1) Removed the thermostat so it runs cooler.
2) Ran 1/3 Seafoam through IM vaccum line, 1/3 in the gas tank, 1/3 in the oil crankcase.
3) Flushed coolant, put in 50/50 new coolant, and Redline Water Wetter.
4) Borrowed used catalytic converter and replaced the old one. (NOTE: Shining a light through my cat and the borrowed used one, compared the two, and found out my cat was clogged like a ****.
5) Cleaned and re-oiled K&N filter on my Akimoto Intake.
6) Bought some Denatured Alcohol from the paint thinner section at Home Depot and poured about 1/2 quart in the gas tank and filled up half way with 91.
7) Retarded timing to 14 degrees.
8) Drove it for about 100 miles before I retested to make sure the Seafoam was out of the system.

Friday: Re-tested and results are:

15mph
HC Max is 89 ppm. Measured at 81.
CO Max is 0.53 ppm. Measured at 0.44.
NO Max is 708 ppm. Measured at 685.

25mph
HC Max is 54 ppm. Measured at 39.
CO Max is 0.51 ppm. Measured at 0.23.
NO Max is 746 ppm. Measured at 272.

I can't tell which of the changes made the most difference. I was cutting it close on the border at the 15mph test. All in all, I think it had a lot to do with the clogged cat, the carbon build up in the motor, the advanced timing, and the cooling system. The cooler the motor the better, but the hotter the cat the better. Since I removed the thermostat all together, there should of been a lot less pressure in the hoses and coolant path since it would be circulating continously. Pinching on the radiator hose after allowing the car to warm up for some time and the high temp I felt by just touching the hose for a short amount of time, I felt that there was still a lot of pressure in the cooling system. Leads me to suspect that maybe the water pump isn't functioning too well or at all. It may have contributed largely to how hot the motor is running and why the NOX levels were so high. Again, NOX is produced when the combustion chambers reach 2500 degrees F or higher. But I'm just guessing. I may change the water pump anyways since it's about time anyway. Hope this helps others with similar smog problems.

-Leo

 

Thanks for all the detailed info. I've been wrestling with my 88 CRX with JRSC for a month now all because of high NOx readings. I've done allmost everything you did except dealing with the cooling system. It does not run hot, but i've just ordered a lower temp (160') T-stat and i'm going to flush the whole cooling system next week. The Denatured alchohol really helped the HC and CO but not the NOx (i added a gallon to half a tank). My Nox at 25mph is killing me ( 1400 ppm ) and i do have a brand new 2.5 inch high flow cat.

Where do you get this "Seafoam" from?

Still struggling the "smog" fight......

 

NOX is produced at super high temp above 2500 f so if you greatly reduce the heat in your cc whether it be to go to colder plugs, retarding the timing, using alcohol or methanol in the tank, change the thermostat, it will help it greatly. The stock cats are 3-way catalysts with one of the elements helping to eliminate the NOX levels. Not sure if your high flow cat is a 3-way or 2-way. Might want to check into that. The Seafoam I got from Napa Auto Parts. Helps to clean out the junk carbon in the motor. HTHs. Good luck.

 

set timing back to stock....get some honda top end cleaner....and try it again.....if you don't pass get a new cat .... and then try again

 

Well, i do have colder plugs and the Cat is brand new( but a high flow unit and it is 3-way.) The timing is retarded and i'm running stock injectors. It has probably been running a bit rich and maybe that has led to carbon buildup even though the engine is rebuilt with only 13k miles on it.

I will try the Seafoam next, along with flushing the cooling system & lower temp T-stat. I'm also thinking, even that it's a new Cat Converter, it's not as good as a OEM unit. I'd like to see a test of OEM converters vs. High Flow converters on actual emissions and not just flow.

 

where can i get top end cleaner?

 

bump