speedball3

I have a stock 97 civic LX, K&N drop-in filter is the only engine mod I've done. The air filter was cleaned recently... the car didn't have fresh oil during the test, oil levels were low (just changed oil after failing). Plugs are old, as are cap and rotor, but neither of those seem to point to how the car is failing. Here are my readings:

15mph:
HC
Max: 66
Meas: 5
CO
Max: 0.57
Meas: 0.13
NO
Max: 487
Meas: 825

25mph:
HC
Max: 49
Meas: 3
CO
Max: 0.55
Meas: 0.12
NO
Max: 774
Meas: 454

So I only failed the 15mph test, which seems strange to me. From what I've searched, high NO is usually the case of high cylinder temps, caused by a bad EGR valve or carbon buildup. I don't think 96-00 civic even HAVE an EGR valve, so perhaps it's carbon buildup, but that doesn't explain why it only failed the 15mph test and NOT the 25mph test...it in fact did very well in the 25mph test. Any clues, ideas?

speedball3

bump

gsrhatch2356

Yes it is actually NOX which is created when combustion temps are 2500+ degrees and the reason you may fail low and not high is cause there is more fuel coming in at higher speeds due to load. there for the gas actually cools off the combustion temps a little. A couple of things that can control NOX on non egr set ups.

1. O2 sensor
if the o2 sensor is not funtioning properly then wont get in enough fuel to compensate for lean conditions (like I said fuel cools combustion chamber) a lean condition actully is what melts pistons. and obvisouly you need to make sure your engine is up to par but looking at the other readings its probally ok

2. Cat
even though the cat is used to mainly compensate for HC and CO it also cleans up NOX and even if it is working but performance is low then it might not clean up enough for the test. always a good check is temp after cat should be 100 degrees hotter then before. give or take a little but one that is only 50 degrees hotter after works but performance is low.

3. Carbon build up
like you said carbon build up can cause high NOX but mainly causes high HC I would run a drip intake cleaner but do it before a new cat is put on and 02 sensor.

these should help your problem, I had a 90-93 integra that was failing on NOX and when I put I new 02 sensor and cat on it was putting out great numbers. and also do not put on a HIGH FLOW CAT!! they may be good for performance but they are not good for emission readings

Good Luck

speedball3

Is that it? Just the cat? Why would everything else be okay? Do you think having a fan on during the test makes a difference? The guy had a fan on, but it was like 20ft away from the front of the car.

RE: The cat.... I'm curious whether I can sneak by w/an aftermarket header.... the engine I have, d16y7, has an integrated exhaust manifold and cat. Buying a new exhaust manifold/cat will be ~460 shipped (via majestic honda). Buying a DC sports header + cat + cat-back would be ab $100 more or so. The question is tho, how complete are smog techs supposed to be? Before he barely looked in the engine bay... any smog techs out there?

thesmogman

YO, did someone ring?

I would say just by looking at the numbers you need an O2 sensor. One other thing that raises Nox is running lean. Your HC numbers are low. Lower than normal creating a lean condition.

If the temp's are above 72 degrees a fan is required and should be about six feet from the car. Tell him to test it correctly this time.

Most smogger's will look for a CARB number on the header or a sticker with it on it. So if you get a CARB legal header for your year and motor then you are good to go.

By the way this CARB stuff is for California.

suspendedHatch

If you put a header in there that isn't 50 state smog legal, they'll automatically fail you. If you're cheap, just keep your stock exhaust so you can swap it back on every two years for the smog check.

I run a Magnaflow high flow cat and I've passed smog 3 times on it.

When O2 sensors fail, they most often run your engine rich, not lean. It depends on whether it completely failed or it's just getting lazy.

What's your ignition timing at? Advancing the timing past the middle point of your spec raises combustion chamber temps causing an increase in NOX. My motor is extremely finnicky with ignition timing. Advance it and you get NOX, retard it and you get HC. I stepped down to a colder plug and it took care of the NOX.

Duane_in_Japan

Checking timing should be madated as part of his inspection, low HC does not say lean, CO is your rich lean indicator, HC is burning well or not. I will not swear that you do not have a EGR Valve but EGRs are a thing of the 80s so I THINK you have one and please be sure that you do or dont and if you do then it seems time to do the ole port cleaning. Also get your car in there with a really hot cat, drive it around in 2 or 3 and get it hot so it can be "LIT OFF" and working at its potential. Ask them to show you how far the fan should be in front of your car in the book please after the test is done, dont waste time while your cat is cooling down. Timing is important, how is your cooling system and fans. Find some Seafoam to do your decarboning, its an old product but its making a huge comeback, it was almost forgotten about, it wont clean your EGR ports if you in fact have an EGR, you have to do that your self.

thesmogman

Thru the years I have seen alot of honda's and I am telling you that 5ppm's and 3ppm's is low. And low HC does mean low hydrocarbons which does mean lean.

CO is mostly related to combustion. Good burn equals low to none, bad burn equals high CO. Like when you run old gas that has been sitting.

A normal HC reading would be near 30ppm's or so for this car. Your test report has an average of the car's tested. Check it out.

Your O2 sensor is suppose to vary from rich to lean 8-10 times a second. A slow sensor will be 3-5 times a second. However they do get stuck at a voltage without throwing a code. Your O2 sensor is stuck seeing a rich condition and your ecu see's this and is trying to go lean to correct it.

gsrhatch2356

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thesmogman &raquo;</TD></TR><TR><TD CLASS="quote">Thru the years I have seen alot of honda's and I am telling you that 5ppm's and 3ppm's is low. And low HC does mean low hydrocarbons which does mean lean.

CO is mostly related to combustion. Good burn equals low to none, bad burn equals high CO. Like when you run old gas that has been sitting.

A normal HC reading would be near 30ppm's or so for this car. Your test report has an average of the car's tested. Check it out.

Your O2 sensor is suppose to vary from rich to lean 8-10 times a second. A slow sensor will be 3-5 times a second. However they do get stuck at a voltage without throwing a code. Your O2 sensor is stuck seeing a rich condition and your ecu see's this and is trying to go lean to correct it. </TD></TR></TABLE>

So far this is the only one this is giving some good info, the fan should deffintally be close to the vehicle and if your HC are low then you probally are running lean but you need to verify your o2 is good first and watch it on a scope for oscillations and volts should go down to at least .1-.2 and go back up to .7-.9 if it is sticking which it can stick anywhere in that band then your not getting proper air fuel ratio. having a lazy sensor just means that the oscillations are slim to none like the man said a good zirciona 02 will switch lean to rich about 10 times a sec one that is lazy may only switch 2-3 times per second and thats why you need a scope to watch these things cause you wont ever get accurate data off of a multimeter. from everything that I have been taught I have always been told

HC= unburnt something (can be fuel, coolant, or oil)
NOX= combustion chamber temps above 2500 degrees ( and egr is not a thing of the 80's they still put them on brand new vehicels and will for many years to come)
CO=incomplete combustion( pretty self explantory)
C02= Perfect combustion
02= Air (duh) when 02 is high and HC are low this is a good indication of lean condition.

with a combination of this data you can track down and find your problem and when you do make sure you get your new numbers so you can see how one thing can effect all the gases coming out. I like to play with our inspection machine all the time infact I used it to set the igintion timing on my distrubter. I just wacthed for HC to go down and CO2 to come up so I knew I was getting better combustion in the chamber.

Duane_in_Japan

EGR, that is what I meant, they have been around mandatory since the 80's you should have one. The nickname for CO is, a rich lean indicator, HC is raw fuel, unburned fuel. Do they not have access to all 5 gases, 4 gases may help, there is a calculator available to decide if you are rich or lean based on 4 or 5 gas readings.

speedball3

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thesmogman &raquo;</TD></TR><TR><TD CLASS="quote">Thru the years I have seen alot of honda's and I am telling you that 5ppm's and 3ppm's is low. And low HC does mean low hydrocarbons which does mean lean.

CO is mostly related to combustion. Good burn equals low to none, bad burn equals high CO. Like when you run old gas that has been sitting.

A normal HC reading would be near 30ppm's or so for this car. Your test report has an average of the car's tested. Check it out.

Your O2 sensor is suppose to vary from rich to lean 8-10 times a second. A slow sensor will be 3-5 times a second. However they do get stuck at a voltage without throwing a code. Your O2 sensor is stuck seeing a rich condition and your ecu see's this and is trying to go lean to correct it. </TD></TR></TABLE>
I agree with gsrhatch.... so far, this the most convincing argument. Reason being: previously, my exhaust manifold was cracked and I was running rich (which caused me to fail my first smog check). So rich that I could see white marks on manifold cracks when I put in on another exhaust manifold (used, but uncracked and newer than mine). The results I posted here are from my second smog test after installing the exhaust manifold, a new secondary O2 sensor, and reusing my original primary O2 sensor. The reason I used a new secondary O2 was the original was stuck in the other exhaust manifold (and I discovered O2 wrenches AFTER it was stripped...). Perhaps it's time for a new primary O2...luckily that is also the easiest solution.

I don't have my smog results in front of me, but I will double check the average measurements for HC. IIRC, my measured is way lower than the average and I remember thinking "ha, good, I passed this one with flying colors!" I guess that's not always a good thing. =P Is there a way to test the primary O2 sensor voltage? It'd be nice to confirm this prior to paying another $32 to retest and fail. How would I get a voltmeter into the wires w/out stripping them?

RE: EGR Valve - I haven't seen anything on my exhaust that would lead me to believe I have one.... can anyone familiar w/D-series or 96-00 Civics chime in on this?

RE: O2 reading: I believe it was 0% for both 15mph and 25mph.

RE: Aftermarket Header - I would use a CARB approved header approved for my year and model, but for a different TRIM. Subtle, but enough to make a difference (LX vs EX... they used different engines).

RE: Timing - not sure what it's set at, but both tests I went to, the guys checked the timing and it passed, so that should be okay.

Oh and some random other stuff I plan to do/did to prepare for my next smog... not sure if I want to seafoam, since I heard you have to change your oil afterwards, and I JUST did that. As long as it doesn't effect my smog results, I don't really care for the seafoam stuff anyway.
Did:
Swapped out old PCV valve w/a newer one (still used tho)
Changed Oil (had around 5k on old oil and levels were low)
To Do:
New Spark Plugs (~30k on current)
Cap & Rotor (not sure how long it's been on those)
New primary O2? (would like to do a voltage check first, to verify and for peace of mind)

Thanks for all the help so far guys!! All this smog stuff has been a pain in the butt and I hope to get it all over with soon. Once I figure out the problem, I'll be sure to let everyone know what fixed it.

thesmogman

Checking the O2 sensor... You really need a scope to get acurate results, however you can use an automotive meter to get your average voltage. Reason is that the sensor's voltage switches 8 - 10 times a second and a regular voltmeter's sampling is 10 times a second you would get inacurate results. As for getting to the wire without stripping use a pin like a T pin or similar and just push it into the correct wire.

You don't have an EGR valve.
No O2 is good
Aftermarket header, They don't care about the trim just the engine size and year.
Timing is really important. Make sure it is at spec or a degree less.

Hope I got them all.

speedball3

Well, it took me some time to fix everything, but I got around to smogging the car a couple weekends ago and got everything all sorted out. Since my last update, I did new spark plugs (NGK Iridiums), new plug wires (7mm "premium" wires from kragen/schucks), new primary O2 sensor, and new distributor cap (couldn't get that pesky rotor out). All that was good for the following results:

15mph:
%C02 14.2
%02 0.0
HC: 15
CO: 0.39
NO: 329

25mph:
%C02: 14.2
%02: 0.0
HC: 10
CO: 0.30
NO: 260

I am way above all the listed averages, but am within passing threshold. The 15mph NO still seems a touch high, 329 measured vs. 487 maximum, but hey, a pass is a pass. I guess that's as clean as it'll run, which is just fine with me. I am happy to hear that engine size and year is the only thing smog techs will check for CARB EO numbers. That means I can for sure install a CARB approved aftermarket header and as long as I get a properly functioning CAT, I should be good to go. Thanks for all the help Smogman and everyone else!!

lillthingz

There is some stuff at autozone called "guarenteed to pass" it should fix all your NO problems. I never had a problem thought, I am a state inspector.