EGR - High NOx tips?

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Hey lehiguy, after just failing the 5th time I'm thinking a v8 swap may be cheaper.

Next up is COHoya suggestion of a thermostat. Just waiting for the truck to cool down and I'll toss that in.
 
Honestly I don't know the temp of the new one - it took 3 dealer stops to find one and gaskets. I'm not optimistic but I've been surprised before when it comes to something like this. I have an appt. with the emissions techs on Friday so with any luck I'll get to the bottom of this. The good news is the truck's running better than it has in a long time.
 
Although it's certainly more of an issue with HCs than NOx, I've found my 80 would pass much easier if I kept it running at high idle while waiting in line at the emissions place. Kept the cats hot and working.

High NOx is usually high combustion temps though. Carbon build up, vac leaks, lean mixture, too advanced timing.

I'm wondering if some octane boost or premium fuel might get those combustion temps down a little.
 
Hey Gumby, the test I just failed with new O2 sensors was premium fuel too after running a can of BG44K through it. Timing should be spot on, I paid someone to do that after replacing all the associated parts. I don't know why I'd have carbon build-up, this truck gets a lot of high speed use. I'm thinking of doing the Sea Foam thing but have never liked the idea.

They control your idle here, send you away to the waiting room while the truck cools down while off.
 
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Scott took the temps before and after the cat and said "It's working 130%" but I can't recall the temps his guy quoted. He suggested the EGR tube was probably clogged, unfortunately he was wrong.
 
I don't know what he would mean by the cat working at 130% other than it was increasing the inlet temps more than it should be. That seems odd and I would press him for more of an explanation and I would ask him if raw gas in the exhaust would be possibly responsible. Did your previous cat(s) fail or did you just replace it/them because you were upgrading the stock exhaust system to a single cat? The original cat that Scott installed at the same time as going to a larger exhaust on my truck failed because it was getting raw gas into it. That was caused by bumping the AFM setting to run way richer than stock. AFM setting is now still richer than stock but much less than it was when the cat failed. Have you looked at your cold start injector to see if it is gunked up?
 
My previous cat didn't fail, he replaced it along with everything else as an upgrade. It's a year old now so my starting place was on his suggestion I bring it in to make sure it hadn't failed. I haven't changed any AFM settings nor have I looked at the CSI which I assumed only affected starting which has never been an issue. What are the symptoms of a bad CSI Steve?
 
Don't put high octane fuel in, don't worry about your cat, RETARD THE TIMING!


It's simple and it worked for me after spending money on a new cat, new egr valve and god knows what else- none of which affected my NOx levels .

Retarding the timing costs you nothing. It worked for me. Take it back about 3 or 4 degrees.

My only caveat is that this is my experience in a chevy Blazer. My Cruiser doesn't get tested for Nox.... :D
 
A leaking CSI, same as a leaking injector, can let unmetered gas into the system, which may or may not be a part of your truck's problem. Either of those situations would also cause higher readings than normal with the other two emission catagories. Do you have the paperwork of your previous emission tests to compare with the current specs? If so, you will see, thanks to Gov Ritter, that standards have been tightened considerably to the point that your 20+ year old truck is supposed to perform better than it did when it was brand new emissions-wise. These standards are scheduled to get even stricter in the next two years in Colorado. Not cool at all.
 
I've got my fingers crossed - going to Ohio e-check for the first time this week with my Arizona import. Hope I don't need all of this good advice but it's there if I need it.
 
I hope that this is an isolated event and that others don't have to read this but thanks to everyone providing some information to those that travel down this path.

It's a shame Ritter's leaving office voluntarily, I'm robbed of the pleasure of voting him out.
 
Conclusion: Replaced the cat today and it passed with NOx at 4.266 of 5.000 allowed. Prior to the cat was the EGR valve, EGR solenoid both of which were bad but made little difference in the NOx numbers. New O2 sensors also lowered it a bit. Thermostat did absolutely nothing for the NOx.

Summary: Don't delay maintenance, it hurts to replace all these things at once.
 
Front Range 4x4 said:
Conclusion: Replaced the cat today and it passed with NOx at 4.266 of 5.000 allowed. Prior to the cat was the EGR valve, EGR solenoid both of which were bad but made little difference in the NOx numbers. New O2 sensors also lowered it a bit. Thermostat did absolutely nothing for the NOx.

Summary: Don't delay maintenance, it hurts to replace all these things at once.
Click to expand...

Are your numbers still on the high side, or is that about normal?


Zack
 
I have no idea what these numbers mean but anyone that can interpret is welcome to tell me.

HC .3756/3.0 Allowed
CO 1.8591/25.0 Allowed
CO2 - 560.3117
NOx - 4.2660/5.000 Allowed

I believe the truck is running lean from what I've been told. Anyone familiar enough with this stuff to explain the numbers?
 
Hey all, been following this thread as I am tracking some of the same problems down.
Failing CA Smog (High Nox):
@15mph (1659 rpm) HC 47(max 196), CO .28 (max 1.39), NO 2285 (max 1465)
@25mph (1665rpm) HC 36 (max 118), CO .20 (max1.19), NO 1310 (max 1325)

Smog techs suggested EGR valve so I'm going through emissions manual tests which have indicated EGR valve, modulator and vtv were bad so I am replacing these but not sure if they are going to impact NOX?
What effect does retarding the timing have on NOX?
 
I finally passed on my 7th attempt. When I did the emissions check I found my EGR diaphragm was cracked and replaced the EGR valve. Barely made a change. Found the EGR solenoid was bad and the EGR not opening so I replaced that too. Again, not much change. They do lower NOx but from my experience not as much as I expected.

Retarding the timing will help but I don't know how much. My suggestion after this experience is to cut to the chase and replace the catalytic converter. Even though it was a year old (small aftermarket/high flow) that passed the exhaust shops temp test they warrantied it and I passed.
 
Thanks for sharing your experience, I'm leaning towards the new CAT as well once I get the EGR functioning properly. Right now might power is stumbling in lower gears and RPM's. I don't think my cat is the original but I have no idea when the PO might have replaced it either.:meh:
Cheers
 
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