NFB- What to do now? Help Please

[Sean 94z28]

Right in the middle of bringing the Z28 back to life, and stupid CA goes and fails SMOG on my econo machine. The S10 runs like a dream, throws no codes, and gets great milage. I am not sure what to think when it passes by such a large margin on most things but fails NOx.

Heres the report:
SMOG Report

Please help, I will get a scan up soon too, but a quick glance at the info didn't show anything to unusual.

Thanks in advance!
Sean

Duh, 2.2L, 5spd, 1994

[Kevin - Blown 95 TA]

Hi NOX is usually related to faulty EGR, faulty cat, overheating engine causing preignition, too low octane gas causing same, too high compression or all corboned up causing high compression, too lean mixture, or too advanced timing.

[Sean 94z28]

NOx flow chart

I found this, check out the flow chart. Timing is comp controlled (direct fire ignition).

Engine stalls if I move the EGR diaphram. Besides, I don't think the comp cycles egr at 1800RPM high w/high engine load.

Does this leave the stock CAT (at 140,000 miles) as the most likely source of excessive NOx?

I am sure there is some carbon build up with the milage, I hope this doesn't mean that "Old" cars are going to start failing.

BTW CA acknoledged that approx. 30% of all cars tested would fail their new and improved test. Thanks CA

Going to start pricing a new converter now.

Thanks
Sean

BTW temp is as rock solid (middle of the gage) as when I bought the truck 2 years ago, when it passed the OLD test with flying colors.

[Kevin - Blown 95 TA]

Originally posted by Sean 94z28
BTW CA acknoledged that approx. 30% of all cars tested would fail their new and improved test. Thanks CA

Maybe you could petition the GOVERNATOR to do something about it!

...and Kalifornia is the correct spelling.

[Sean 94z28]

I hear ya about this place. The career scene pretty much directed me here back in 96. Or was it the woman I met through said job.

Anyway, I kind of keep my politics to myself around here because I learned how useless it was trying to present logic in your opinions on the left cost. Let's just say I feel like were not part of the USA on many occasions. And I am not cool with that.

Sean

PS. My family's heartfelt thanks goes out to our Men and Women in the Armed Forces. We are behind you 100%.

[Kevin - Blown 95 TA]

I'm sorry it's that way, too. I lived near Sacramento (Beale AFB) in the 60's when my dad was in the Air Force and in San Diego in the late 70s when I was in the Navy, and it was, by far, the nicest place I ever lived. Also the cutest girlfriend I ever had was from Imperial Beach. But, even back then, I had MAJOR trouble getting my car registered. They were so screwed up that they ended up registering it by mistake. The company I work for makes small engines - we make more than GM, Ford, and Chrysler combined - but due to the new regulations in Kali which double the cost, we're considering having the Kali engine models made in China...

[Sean 94z28]

Sorry to bring this up again, but I need the truck to finish the Z.

Yesterday I actually paid a shop to diagnose this problem ($80-you can't do it yourself because the repairs won't count towards your $450 max). They determined it was the EGR - they wan't another $90.

My ? - What is the "EGR system" doing to reduce chamber temps at 1800 RPM and simulated 15MPH. AutoXRAY says the EGR duty cycle is 0% for those conditions. Is there supposed to by EGR cycles under these conditions?

Don't really feel like shotgunning until I reach $450.

Thanks for tolerating the Qs. A lot more intelligent answers here than most places.

Sean

[Joe 1320]

Have you tried the "smog pass in a bottle"? There are a few products that help clean out all the residual crap that commonly cause you to fail the test. They even come with a money back guarantee if it doesn't work. I've seen it work on cars that were in a good state of tune, yet were still failing the sniffer test. It will not correct for major malfunctions, but for your situation it may just be the ticket. You add it to a tank of gas and drive it 'til the tank is done. Refill the tank and go for the test. For $8 it's worth a try.

[Kevin - Blown 95 TA]

Originally posted by Sean 94z28
My ? - What is the "EGR system" doing to reduce chamber temps at 1800 RPM and simulated 15MPH. AutoXRAY says the EGR duty cycle is 0% for those conditions. Is there supposed to by EGR cycles under these conditions?Sean

The EGR system works by letting exhaust gas into the intake and cooling the combustion chamber temp. EGR can be tested with a vacuum pump to check the diaphragm and also by pushing on the diaphragm to manually open it and let exhaust flow into the manifold. Malfunctions include carboned up (plugged) EGR valve, carboned up manifold port, modulated solenoid not working for whatever reason, ruptured diaphragm, bad vacuum line. It is hard to get it to turn on when you want, because the PCM needs to see certain criteria like load, timing, etc. and it is hard to see just looking under the hood, but you should be able to get it to go on driving around with a scanner - although this was hard to see in my car too.

[N20LT4Bird]

I agree with Kevin; the EGR is the main system responsible for NOX reduction. It reduces combustion temps by introducing an inert gas to the mix. High combustion temps are the cause of NOX production. Maybe this is dumb, but could you hook your EGR up to a constant vacuum source and test NOX levels? This might throw a light?? If your auto X-ray is saying the EGR has a 0% duty cycle at 1800 rpm and the test requires less oxides of nitrogen then, it may be your problem that the PCM is not cycling the EGR. If you hook it to a constant vacuum, you just gave it a 100 percent duty cycle. Like I said, probably wont work, but maybe something to mess with. You could see what NOX levels drop to with a 100% duty cycle. Then, you have to find out why the PCM is not cycling the EGR. Or, as mentioned before, you could be running a bit lean, causing excessive heat in the combustion chamber. What are your O2's doing?? You may need to check fuel delivery. The injectors may just need a good cleaning?

[lower et then u]

TRICK TO PASSING

100 OCTANE 1/4 TANK AND 1.5 GALONS OF METHANOL TO RUN THE TEST THAT SHOUD DO TH TRICK I DO NYS THIS WORK'S ALL MOUST EVEY TIME. AFTER PASSING THE TEST GO FILL UP TO A FULL TANK OF GAS.

[Sean 94z28]

Update: Passed

Tune up:
Fuel Filter (pressure was ok though 41psi before and after)
Air Filter (put stock in place of oiled aftermarket - not a KN)
Oil Filter and fresh oil
PCV valve (not really related but it was old)

= $35

New Catalytic converter (original, w/ exhaust leak at outlet)
New muffler (multiple rust holes and only $60 installed with CAT)

= $340 (bought a higher capcity cat for V6 engines)

Total $375
Result: CO max allowed 592
failed at 768
is now 512

Thanks for your inputs!

[Mirroredshades]

Glad you made it! Too bad it was such a PITA.