Hey guys I have failed smog twice due to high nox . I have takenTwo test and the second I almost passed I just need some help to what I could look for .

This car is a 97 civic hatch i bought it with a blow motor swapped in jdm d16a but other than thats its stock

First test: timing was set to 12 btdc

Mph15: co2:14.3.
O2: .3.
Hc :28 max 49 .
Co: .29 max.57
No. 702 max 487.

Mph25: co2 : 14.1
O2 : .3
Hc:35. Max 66
Co: .36 max .55
No : 756 max 774



After that I change spark plugs to heat range 6 NGk they had 5 before . , changed throttle body for a known working one ( had problems with tps on my old one ). Pcv valve, and top o2 sensor (denso) went back right after

Second test at 12 btdc

15mph: co2 :14.2.
O2. .2. O2:.1
Hc : 11 max 66.
Co: .36. Max .57.
No: 553. Max 487.

25mph co2: 14.3
Hc: 11. Max : 49
Co : .39. Max :.55
No: 578. Max: 774

i went for a third time but this time i beat it for like 20 miles i got preety much same number except i got the hc down to 6 for 15 mph and 8 for 25mph and co went down to .23


i was thinking of changing thremostat and flushing the system and retarding the timing to see if that work could it be the cat any advice will be awesome

 

Hmmm, pcv valve? what state are you in??? my Hc is 95, max 92 and my NO was 916, max is 776.....bought this car swapped with a d15bz1 and an auto trans, any tips to reduce my emissions is great

 

You might also try replacing the fuel filter, in addition to the thermostat. If the problem persists, the cat may be bad.

 

turn your timing down to 10btdc. you are allowed to have a tolerance of +-2. and change your fuel filter or run injector clean or some kind

 

One trick you can do to refresh your cat is to do a citric acid bath. Pull your cat off and find a tub or bucket it will fully submerge in, then mix up a citric acid bath and let it soak over night. Drain it and you can blow air through it to dry it out a bit faster.

Citric Acid is one thing shown to refresh older borderline catalytic converters.

Google citric acid catalytic converter and you should find a wealth of information on it.


It appears you need to keep the citric acid warm.

 

The fuel filter has 2000 miles on it I put the filter on when put in the jdm motor . I also check fuel pressure 32 with vac line on 43 with it off

 

I thought retarding timing lowered nox not advancing it

 

The citric acid stuff sounds nice but I would be a bass because the cat is on the manifold .. I found an rsx cat and was thinking of just adding on just for smog and if it passes by Alot then I will just get the y8 header and keep the rsx cat

 

Will the there be to much back pressure if I leave both cats on or would it be ok ? Also would the rsx cat work well

 

Bump for the if rsx would work goon on a civic

 

it should lower all your emissions just a little but seeing that youre failing in nox at 15/50, just retard it a little and that will should bring everything down a tad.

 

I agree with lowering the ignition timing to the low side of spec.

Also try running high octane, flushing the coolant, and you may even want to replace the thermostat. Some come with 82C (180 degrees) but 170 is the recommended temp.

Does your radiator fan come on? Are they using the dyno fan when running your emissions test?

NOx means your combustion temps are too high so anything you can think of to lower it will help.

 

Run your car til empty. Do a 1:1 mix of methanol and regular unleaded. Drive to the emissions test and pass. Go fill your car up to full w/ regular unleaded and worry about the problems when you have the time and money. Done it with success 3 times now. Literally your car will blow zeros.

 

i will try it and post how it worked out thanks

 

i already replaced thermo stat and flushed and retarded timing to 14btdc but it went down only like 10 points and failed still lol

 

you guys think that e85 and and y8 injectors would work

 

I dont think i add enough Methanol to gas and i also unplugged the vac line from fpr to increase pressure ..... It did go down to 514 i needed 487 to pass i dont think i ran it enough either ....i think my car had like 1 1/2 gal and added 84fl oz of meth should i add more ?

 

ok i tested agian but different then my usual i added a gallon of meth (yellow heet ) and gallon 1/2 of 87 and fail but nox was at 732 before i had it at 514 with just 87 .. i also turn on the rad fan to be on and disconected the vac line from fpr to be at 42 new themostat and flush system i bleed the system .. i dont understand what could it be that cat be clogged ?

 

also co went up almost to failing so that menas its rich because of the fpr and rad fan being wired on nox is suposed to go down not up to 733 from 514 ? need help i have already taken 6 tests