here's the deal, i just bought a 91 SI and it failed smog 3 times. there are NO cel's on and everything is straight stock but the headers(dc). the motor is a D16A6 w/ a PM6 ecu. i'm stuck with a perfectly good car that doesn't pass smog. i put on new wires, spark plugs, fuel filter, distributor and air filter. i also did a compression test and it's all good. anybody ever have this problem? or would know what it could be?

would it be the o2 sensor? or header? also i noticed that on the headers the 02 sensor is only on one section of the tubing. could it be that the o2 is not getting a propper reading?

any info or advice would be appreciated.

 

Which part of the smog did you fail?

 

ASM Emission Test Results

NO (PPM)
MAX AVE MEAS
835 237 1343
774 199 1482

 

So you ust failed your NOx? That won't be the header...... How old is your cat? Look into that, and also look into flushing carbon deposits out of your combustion chambers. One way is to spray a mist of water into the TB. You can search on that.. "combustion chamber cleaning"

Or seafoam.

Also I was just like you.... stock but a DC header. I did take off the header, but it only lowered my CO and HC. I had to get a combustion chamber cleaning to pass.

Good luck!!

 

Dude check the egr valve! (just kidding) It isn't running a bit on the hot side is it? Most times it's the cat. Check timing too.
-Brian

 

some good advice so far.......THANKS for the feedback.

 

If you're failing nox with a stock engine the first thing I'd look at is the cat. The header shouldn't really affect emissions because a dc header is carb legal.

 

is that smog crazyness only in cali???

 

Ok from what I have seen the SOHC dc header has the O2 bung down behind by the cat.? If this is the case then it will run diffrent because the non heated O2 is so far away from the heat. I would say it would prolly be richer. I dunno if this has anything to do with your test or not.

Sorry I'm in Utah and we do not have emissions here, just trying to throw out ideas.

 

^^^ Mine's closer to the stock header location

 

Check your cat. It might be dirty or clogged up with carbon. That's what I replaced.

-Jon

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DohcVtecCrx &raquo;</TD></TR><TR><TD CLASS="quote">Ok from what I have seen the SOHC dc header has the O2 bung down behind by the cat.? If this is the case then it will run diffrent because the non heated O2 is so far away from the heat. I would say it would prolly be richer. I dunno if this has anything to do with your test or not.

Sorry I'm in Utah and we do not have emissions here, just trying to throw out ideas.</TD></TR></TABLE>

yeah the o2 is running rich. i believe i have an older style dc header so the o2 is only on one section of the tubing. why they(dc) did this i don't know? i have a feeling that's the problem though.
cali smog sucks and to top it off i have to bring it to a "test only station"
i'll keep you all updated.

 

headers won't cause one to fail the NOX test.

could be bad cat.

 

Most likely its running rich and all those carbon deposits as a result are raising ur combustion chaimber temps.... = hi NOx. That's the way I see it. Since you're bay area I can refer you to the people that did my cumbustion chamber cleaning which lowered my NOx from gross polluter to passing if u want. That route was much cheaper than replacing the cat... PM me

 

FINALLY PASSED! but almost failing smog again.

i ended up swaping and borrowing my buddy's piping. from header to exhaust and that fixed my problem. most likely it was because of........

1 - it was an older style dc header(sensor is on the top side of the header instead of on the bottom part where all the sections meet) so with a higher mileage motor caused my emmisions to go up. for dc.

2 - i had on a no name/brand ghetto cat that was on there.

Modified by BlUeDC2nEr at 7:23 PM 12/28/2005


Modified by BlUeDC2nEr at 7:25 PM 12/28/2005