Civic failed emissions testing: super-High Nox

Ok guys, please help a damsell in distress...
Got a 93 Civic Cx (5 spd hatchback), tried twice to e-test it, but failed.
Both times all the other readings were amazing, but Nox failed miserably
(do I really need to find the papers and give you the exact numbers?)
First time didn't do anything, and Nox were double the allowed, so I got a
new (3-way) cat put in, booked another test, run it for an hour to make
sure she was all warm and fuzzy and went in... this time Nox 4 times the
allowed!!! What's going on???!
I know, your'e going to suggest a faulty EGR valve, but my car doesn't have
one. So... maybe it be the rad? It's pretty raggedy...Or thermostat? (Still
original)
Anything else? It's got almost 260k on it, and the oil has been changed
every 5k, the engine is clean as a whistle.
It has a stainless steel exhaust and a custom made muffler, but those
shouldn't make a difference, should they?
Maybe my timing is off? Would there be any symptoms?
I'd really appreciate any advice; I hate it when they try to screw me over
just because I wear a skirt!

 

Wouldn't a faulty O2 sensor cause ALL of the readings to be high? (Not just
the Nox, like I have). And besides, I don't get any trouble codes.
Please don't tell me it's the head gasket?!! There is a little bit of white
smoke, but it doesn't smell sweet, so I'm assuming that's just condensation.
I've been surfing all day trying to get answers to my problem, and I sure
have learned a lot, but I'm still confused as to what is causing the high
NoX!!!Heeeelp!

 

It would help...

The idle test does not measure NO, but tests at speed do. We need to know
those results.

Did you IDLE it for an hour, or did you subject the car to a high-load
drive for an hour? BIG difference. And how long did it sit before they
actually had it running on the dyno?

That's right! Only the automatics got EGR.

Do you look good in the skirt? Just asking...(I'm already married
anyway...)

Nitric oxide emissions are caused by combustion temperatures that exceed
2,500deg F. If you're failing smog due to high NO, there are several
possible causes (the cat *apparently* having been ruled out):
1) Ignition timing too far advanced
2) Excessive combustion chamber deposits (unlikely unless car has been
woefully maintained)
3) Poor cooling (gauge reads high)
4) Lean combustion due to old or defective oxygen sensor
5) Lean combustion due to clogged injectors
6) Defective new cat (it happens!)

 

At 40 km/h

Limit reading
HC ppm

 

40 KM/ h
Limit Reading Result
HC ppm 82 11 pass
CO% 0.45 0.01 pass
No ppm 0636 2431 Fail (no kidding! ya' think?!)
RPM 1867 Valid
Dilution 14.51 Valid

Curb idle

HC ppm 200 8 pass
CO% 1 0.00 pass
NO ppm N/A N/A N/A
Rpm 744 Valid
Dilution 13.10 Valid

And before the test I drove it around a small strech of highway, then city
speeds, then it sat maybe 5 minutes idling. It took the guy about 10
minutes to hook the car up (why so long, i have no idea, he was standing
around scratching his head). Hope this helps! Thanks so much for all your
help!
I keep thinking it must be my O2 sensor (still orig.), but then again,
wouldn't it affect the other readings as well (+ cause a trouble code?)
So the maybe the rad, then? ....oy vey, I don't know what to do! Better
go to sleep now! Thank you again!

 

------------------

Search this group to see if PCV is ever cited as a cause. I know it can
certainly whack out the idle, as well as sucking the oil out of your
engine / messing up the CAT.

P.S. Good idea to post to your existing threads, rather than starting
new ones each time. :-(

'Curly'

 

:

If the O2 sensor indicates less O2 in the exhaust that what you really
have, then the ECU would respond by making the mixture leaner than
normal. Lean mixture means lowered HC and CO, and increased NOx.

There is an article on NOx failures at
http://www.aftermarketbusiness.com/aftermarketbusiness/article/articleDetail.jsp?id=106701

=======================================================
A very modest collection of Honda tech info can be found at:
http://www.geocities.com/ng_randolph

 

What an excellent link. I've bookmarked it.

It seems an exhaust leak can cause high NOx as well as an old/defective O2
sensor.

Interesting that the tech says cooling system problems and combustion
chamber deposits do not cause increases in emissions.

 

Well, I got a new o2 sensor put in this morning, got re-tested and she
passed no problem! Thank's everyone, I really appreciate all your help!
XO -Lady (who looks damn good in a skirt!)

 

:

Ah, come on; You can't write that and not post a picture!