My 85GT did not pass smog today. HC and CO were very good but the Nox was way too high. I will post some numbers later but in the meantime, what should I be looking at to get the numbers down? Before you ask I have just put in a new Walker cat, Bosch 02 sensor, new EGR valve, new spark plugs, ran Seafoam through it, used Guaranteed To Pass but still has high Nox. Your input? Thanks, Kit
What engine do you have? If its an 2.8 its your o2. They don't like the Bosch it reads to slow try getting a Denso. I logged mine and it was horrible and once I switched to a Denso no mere lean and pig rich issues on my car .you can also check your base timing and make sure its correct.
[This message has been edited by soldier_263 (edited 04-05-2014).]
You guys mentioned two very important things. The smog guy said my car was definitely running lean and that the timing was slightly off. He said it was at 6 degrees when it was supposed to be at 10, although he said it's not off enough to produce such high Nox. Ironically I have only recently been using Bosch 02 sensors. I had been using Denso from Rockauto. By the way, not sure if this matters but your supposed to run the Guaranteed To Pass all the way through a full tank but didn't have the time. So , I basically only burned up a 1/4 to a 1/3 of a tank. There is a lot of it still in the tank. Is it affecting my Nox numbers??
Kit, let me know how this turns out. Back in 2006 my Fiero failed smog because of the same issue. Everyting else was just borderline failing. I never ended up getting the thing smogged so let me know what you find. My big fear is that California will continue to tweak the numbers so we never can smog these cars again.
Ok, here is the Nox numbers : At 15 mph: Max is 804, Average is 413, Measured is 1938 At 25 mph: Max is 695, Average is 342, Measured is 1656 Mine is the "Measured" numbers.
Ok, here is some more info: Within the last 7-8K miles I have replaced the fuel pump, reconditioned fuel injectors, powder coated upper plenum and middle intake, fuel pressure regulator and cold start injector.
Ok, here is the Nox numbers : At 15 mph: Max is 804, Average is 413, Measured is 1938 At 25 mph: Max is 695, Average is 342, Measured is 1656 Mine is the "Measured" numbers.
When my iron duke reported similar numbers, my pre-cat O2 sensor was not outright in a failed state, but it was reporting incorrect voltages.
My NOx was also high when SMOG tested 3/21/2014. But strangely, my report says that the max allowed at 15mph is 565, and the max allowed at 25mph is 522. Weird how our max allowances are different when we only live 40 miles from each other. Typical CA BS.
Anyway, at my last test (2 years and 10k miles ago), my NOx readings were 3 at 15mph and 6 at 25mph. Hard for me to believe that 10k miles later im showing 282 at 15mph, and 9 at 25mph. The only change I made was installing a NOS, OEM EGR valve.
After you replace that O2 sensor, and correct the engine timing. Please let us know what the results are.
My NOx was also high when SMOG tested 3/21/2014. But strangely, my report says that the max allowed at 15mph is 565, and the max allowed at 25mph is 522. Weird how our max allowances are different when we only live 40 miles from each other. Typical CA BS.
Anyway, at my last test (2 years and 10k miles ago), my NOx readings were 3 at 15mph and 6 at 25mph. Hard for me to believe that 10k miles later im showing 282 at 15mph, and 9 at 25mph. The only change I made was installing a NOS, OEM EGR valve.
After you replace that O2 sensor, and correct the engine timing. Please let us know what the results are.
Looking for more input please. Also, In order to keep this thread alive and more interesting (and because I really need to get this lean issue solved) I would to post a few pics of my 85GT. I am very proud of her. But, can someone post the pics for me ? I need someone's email to send them to. Thanks, Kit
I have never figured out how to post pics on here. However, I do know that vacuum leaks are very common with our cars. A vacuum leak will cause a lean condition. After you dump that Bosch O2 Sensor, check all of the plastic vac. lines and their rubber connectors.
High NOx is common if your EGR system isn't functioning properly. Check to make sure that the vac. lines going to the solenoid and then to the valve are connected properly and are not leaking. Then, with the engine running, manually open the EGR valve to see if the engine stumbles and stalls. If it doesn't, then you have carbon blocking the EGR passages. If it's an aftermarket EGR valve (Standard is a common replacement brand) check to make sure that the correct size washer was used. Maybe the installer used the wrong size washer and even though the EGR system is working properly, it can't get enough EG to R
When was the last time you replaced the fuel filter? Highly doubtful, but maybe it's clogged and you're simply not getting enough fuel.
What's really odd about this is the fact that you are not experiencing any drivability issues and you're not getting a service engine soon light with a lean or other code. Makes me wonder why that O2 sensor isn't recognizing the lean condition.
So, check for vacuum leaks, check EGR function, swap out that O2 sensor.
[This message has been edited by donuteater306 (edited 04-06-2014).]
Ok, thank you for that input. I will order a Denso 02 soon. Will also do a EGR valve check with engine running as you mentioned. EGR brand is Autozone which is actually a Wells. I used the correct #11 (going by memory here) orifice washer according to Bloozberry here on the Forum. I will also check for leaks around the EGR solenoid and under manifold lines. However , I do not have high idle issues and the car runs beautifully with nary a hiccup , cough or burp. Kit
No problem. Ya know, If I recall, a Wells EGR valve may not have a big enough opening underneath the diaphragm to get your fingers in there to manually open the valve. You may need to use a hand held vac pump.
Like you, I don't understand how the numbers could be so far off yet it's running perfectly fine. No misfire, no shaking, no stumbling.
Like you, I don't understand how the numbers could be so far off yet it's running perfectly fine. No misfire, no shaking, no stumbling.
Ironically that is the same problem with my car. I used the Bosch O2 sensor and it ran perfect, idled perfect and drove fine.......but failed just like Kit's car did.
My NOx was also high when SMOG tested 3/21/2014. But strangely, my report says that the max allowed at 15mph is 565, and the max allowed at 25mph is 522. Weird how our max allowances are different when we only live 40 miles from each other. Typical CA BS.
Anyway, at my last test (2 years and 10k miles ago), my NOx readings were 3 at 15mph and 6 at 25mph. Hard for me to believe that 10k miles later im showing 282 at 15mph, and 9 at 25mph. The only change I made was installing a NOS, OEM EGR valve.
After you replace that O2 sensor, and correct the engine timing. Please let us know what the results are.
Update for today: I replaced the almost new Bosch 02 sensor for a Denso, then adjusted timing to as near 10 degrees BTDC as I could get it. Then, I took it to my smog guy and it still has very high Nox. The good news is this guy smogged my other Fiero, so he knows I'm a real car guy and that I'm trying really hard to comply with the law. (He is starting to feel my plight & frustration) He gave me several pointers on what to check and he even tested my EGR valve and put my 85 on his rollers. Anyways, here's what he told me to check: (because my car is running VERY lean: Coolant Temp Sensor operation, clogged fuel filter, vacuum leaks/intake manifold leak, look for exhaust leaks.
Forgot to mention one more thing. Engine tends to run a little warm so I took the thermostat out to make the engine run cooler than normal to counteract the very lean running condition. Funny, even with the thermostat out the fan will still come on when you're in stop and go traffic. Brand new water pump and radiator around 15K miles ago.
More input please...these high nox numbers are going to force me to apply for a non-op. Kit
Update : my car finally passed! . Turns out that whatever controls EGR vacuum was at fault. My smog guy said the EGR valve is opening too far or maybe he said too much? At any rate, to get it to pass I had to plug the vacuum line that goes to the EGR valve . After that it passed with flying colors.
Question: Will it harm anything if I leave the vacuum line ( that goes to the EGR ) plugged? What controls EGR vacuum? I need to look at that . Thanks.....
What did you wind up doing? Did you get it to pass? I have an '84 Duke in Orange County and I just got almost the same exact numbers as you. HC and CO were great while NOx was over twice the limit. I had replaced a lot of the same parts you did (new cat, newish plugs, some other things). I'd really appreciate an update, as I have two weeks to retest.
I'm hoping it's just my hot-running condition. I'm going to try a radiator flush to remedy that.
