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!
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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!
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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!)
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At 40 km/h
Limit reading HC ppm
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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!
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"Lady via CarKB.com" wrote:
<snip>

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 6701
======================================================A very modest collection of Honda tech info can be found at: http://www.geocities.com/ng_randolph
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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.
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Lady via CarKB.com wrote:

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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'
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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!)
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"Lady via CarKB.com" wrote:
<snip>

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