smog question

[First2Finish]

if my car is fine at high rpms during the breather test and failing at idle what does that mean? or is there no real 1 anwser fix for that?

my mods during the test included
stock airbox
dc headers
hi flo cat, enlarged piping.
6month old cap and rotor, stock timing.
thats all

im guessing that its the cat thats giving me problems.

if it helps at all its a honda, sohc.

[N1240SX]

They didnt tell you anymore details on why it didnt pass at idle?

[First2Finish]

nope they didnt tell me anything. well the only thing they said was its the cat, but i want to be sure.

[N1240SX]

Well (Correct me if im wrong) but i think your Cat needs a certain amount of pressure on the side coming from your headers to work right... If it does not get that then it will not function properly...

So in short you may not need a high flow cat on your car...

(This might be better in the tech section)

[SpeedRacer20]

If you failed CO you may be running rich, my SR ran very rich at idle and I never did pass emissions. I was off by .05%

[WIKKEDSOL]

I agree with PC. I think you should let your car run for a bit to warm it up. I failed at idle before also because I drove it to Arco down the street and the car was only on for about 5 minutes. But I was also running rich so most of the Hydro Carbons ate up my cat. Well...... it disintengrated the honeycomb looking stuff inside.

[HondaThis]

Originally posted by SpeedRacer20
If you failed CO you may be running rich, my SR ran very rich at idle and I never did pass emissions. I was off by .05%

Hydro Carbons are unburned fuel... A better way to help this guy out is for him to let us know what category he failed in.. and by how much.

If your engine isn't hot..... don't smog it... a few bumps off the rev limiter before testing does wonders!:D

[Turbo Geo]

the car failed at idle in the hc part.

was at like 500 or so give or take.

[Ritz S14]

I seriously don't recommend anyone doing this, unless they have done it before. Cuase sometimes you'll make it worse than it already is. 500HC is a damn lot, passing should be around 120ppm. 500HC if you lived in CA would make your a gross polluter. HC and C0 work with eachother, so if you lower the HC by adjusting the mixture control screw your C0 will raise, and can cause you to fail the test as well. Best way to figure out the air/fuel ratio is by using a 4 or 5 gas analizer.

HC (Hydro Carbon) = Rich Fuel Mixture
C0 (Carbon Monoxide) = Incomplete combustionra
NOx (Nitrates of Oxygen) = Temperatures above 2500F

[SpeedRacer20]

Yeah if your failing by that much you have a bigger problem on your hands. You should have it checked out by someone, the idle air/fuel screw wont change too much. Especially if your saying 500ppm. All the screw really does is raise the rpms.

What kind of engine is it? a Honda...?
When I used to own a honda SOHC my car passed with extremly high flying colors.

[HondaThis]

But... you may have bad valve seals and/or rings if you're running at 500.. A fuel presure regulator would help too.. just lean it out a bit! :D

[SpeedRacer20]

Originally posted by PC
no that screw will change alot and it raises rpms by letting more air in at idle. i know cuz i have a test report of my car that had similar problems and i adjusted the screw some and it went back down. my HCs went from like 550 down to 211 and 212 was passing all by adjusting the idle air bypass.

Well it does absolutely nothing on my car, I went from 1.3% CO at 575 RPMs to 1.25% CO at 850 RPMs. Passing was 1.2%. I also added a new Cat.

[Dilmeet]

its simple my friend had the same exhaust mods, heres what he did, got a smog shop's After Market exhaust (they pass smog) for sure. and he put on his stock headers and left the piping the way it was.