danny951

I just got the car tested for emissions here in Texas. I failed miserably for the first time with my current setup. I have a fabspeed 3" downpipe back exhaust, no cat (they don't visually inspect), and guru chips. I don't think chips matter since the low speed is closed loop straight from the O2 sensor, but I thought I'd at least put that in there. I know others pass with flying colors with guru chips and I have passed in previous years. Here are the results:

Low Speed (15mph):
HC (ppm) Max: 167; Mine: 191 (FAIL)
CO (%) Max: 0.94; Mine: 0.64 (PASS)
NOx (ppm) Max 1273; Mine: 2996 (FAIL)

High Speed (25mph, 2nd gear)
HC (ppm) Max: 162; Mine 173 (FAIL)
CO (%) Max: 1.04; Mine 0.74 (PASS)
NOx (ppm) Max: 1163; Mine: 3199 (FAIL)

I am just off the charts on the oxides test. I do think I'm running way rich also. O2 sensor? Please help!

danny951

I'll also add that I do think I have been running rich. YOu can really smell the gas smells from the exhaust when they were running the tests. So much that I had to leave the garage area. Additionally, every now and then, say once or twice every couple of weeks, when I start the car, the idle is very rough, and the RPMs bounce a couple hundred RPM like the motor is trying to settle down.. it will do that for a minute or so then settle down, or i can rev it a little and it will settle down at a nice idle. O2 sensor related?

JC951

i'll bump this...mine just failed too...although here in CT our CO% is .64 max and mine was .92 at 25mph. The NOx max in CT is 1400 and i scored a lovely 1447.

ryanm6100

This is exactly why I have yet to register my 951 in Texas.

(no cat, APE II chips)

TroyN

Found this on the interwebs, so take it w/ a grain of salt!

“A lean air-fuel ratio results in high cylinder temperature and excessive NOx emissions…. A lean air-fuel ratio may be caused by low fuel pump pressure, partially plugged injectors, a vacuum leak, or defective O2, MAP, ECT, or IAT sensors. A lean air-fuel ratio causes high NOx, high HC, high O2, and low CO and CO2.”

Darwantae951

Hey Danny, I bought a 3" slip in cat from SFR. If you want to borrow it to put on, maybe we can work something out.

danny951

I had the O2 sensor tested and it failed, so I replaced it just now. The inspection place already closed so I'll have it retested tomorrow and see if that's all it will take. Thanks Darwin for the offer. I'll see how it runs tomorrow and let you know if I need to borrow it for the inspection. Funny, I found my results from 2008 and they didn't even test NOx.. I went by with the result sheet and showed the guy and he wasn't sure why that would have been, but perhaps they didn't have their dyno up and running yet (new shop). Strange though...

danny951

Re-inspected today and still failed. Numbers look better, but I'm still way off. To this point I've merely replaced the failed O2 sensor. It appears I've still got something wrong on the car aside from not having a cat. You can still smell the exhaust pretty strong, but it's not nearly as "rich" smelling. I'm open to suggestions of what else to check that could cause high NOx numbers. My HC's are under control now, so the O2 sensor did help there. I'm also going to give you a call, Darwin, about borrowing that converter and hopefully sneaking by my next inspection.

Low Speed (15mph):
HC (ppm) Max: 167; Mine: 129, down from 191 (PASS)
CO (%) Max: 0.94; Mine: 0.74, up from 0.64 (PASS)
NOx (ppm) Max 1273; Mine: 2557, down from 2996 (FAIL)

High Speed (25mph, 2nd gear)
HC (ppm) Max: 162; Mine 122, down from 173 (PASS)
CO (%) Max: 1.04; Mine 0.70, down from 0.74 (PASS)
NOx (ppm) Max: 1163; Mine: 2662, down from 3199 (FAIL)

ilikemy944

NOx = cat.

KuHL 951

I don't think you'll ever get NOx down without a cat on during the test. I just went through this on 2 cars in a row. If you ae stll running an AFM make sure the flapper is closing all the way and closes pretty firm; a weak spring will allow excess air in and throw the AFR off

clangjr

My car passed in MD without a cat, no problems at all. If you need it, I can pull the report when I get home.

KuHL 951

That might be but it looks like Maryland only checks emissions at idle and the standards must be pretty loose if they didn't spot a missing cat on your car. His test is stricter and similar to ours in California and sounds like it's done under load on a smog dyno.

Maryland Emissions

Dougs951

Or run historic/street rod tags like I do.

Or lower it to the point that it cannot get on the tester, they will give you a waiver.

MD has a lot of loopholes.

clangjr

They require you to run the engine at about 3k rpm's while they have a sniffer up the tailpipe. They want you to put it on a roller, but I always talk my way out of it.
Chuck

87_951_Turbo

you should double check your fuel pressure. I had the same problem, turned out to be a bad regulator.
I live out in california, and they are hard-***'s on smog. If you have and chips pull them and put the stock ones back in. Throw on a new cat and drive it straight to the shop! Good luck!