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Failing NOx test for Texas Inspection

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Bigmoose153

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I'm failing the vehicle State Inspection for NOx for my all stock 1990 full size blazer. Below are the results.

Standard for high speed -946/blazer is blowing 1100
Standard for low speed - 1046/blazer is blowing 1907

Any suggestions on where I should focus? Exhaust is still the original and the blazer has 147k miles.
 
Do you have catalytic converters on that truck?

Any check engine codes?

Stock motor?
 
Here is what I always check when one fails.

PVC valve good?
Oil change recently?
Tune up recently?
Timing set correctly?
Check engine light on?
If you have a air pump, is it hooked up and working?
Any vacuum leaks?
Does it run well? No misses or not running real rich?
If that all checks out, I replace the catalytic converter.
I've replaced catalytic converters on about 4 vehicles that failed or almost failed the prior year and they all have passed with flying colors afterwards. But I made sure all these other things were in order first.
 
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michael0584 said:
Here is what I always check when one fails.

PVC valve good? I changed it a year ago
Oil change recently? It's been a year, but only put 3500 miles since the change.
Tune up recently? Its been a year
Timing set correctly? It was when I checked last year when I tuned it
Check engine light on? No
If you have a air pump, is it hooked up and working?no air pump
Any vacuum leaks? None
Does it run well? No misses or not running real rich?it runs well, idles smoothly.
If that all checks out, I replace the catalytic converter.
I've replaced catalytic converters on about 4 vehicles that failed or almost failed the prior year and they all have passed with flying colors afterwards. But I made sure all these other things were in order first.
Click to expand...

Appreciate everyone's response. It does have a Cat but again, never replaced and EGR seems to work via usual tests and I did replace last year as well. Also, stock/original 5.7l
 
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If you have a infrared thermometer, you can test the cat once it's warmed up. Check the temp at the inlet and outlet. The outlet should be about 100+ degrees hotter.
 
I also hate to do another tuneup ( plugs, etc...) if I don't have to considering I've only put 3500 miles since the last tuneup. But I will if that's what it takes but wanted opinions on what to focus on before doing that.
 
michael0584 said:
If you have a infrared thermometer, you can test the cat once it's warmed up. Check the temp at the inlet and outlet. The outlet should be about 100+ degrees hotter.
Click to expand...

I do actually, I'll do that next. Should be different immediately after its been warm for awhile?
 
remove the EGR valve, clean it real good, reinstall, see what it does.

My mothers truck failed one year in Arizona, that's all I did to the EGR valve and it passed very easy.
 
Ok, was finally able to get the Cat temp inlet/outlet readings...

Inlet: ~305
Outlet ~293

Those readings jumped around +/- 5-7degrees.

So bad kitty?
 
Does the entire state of Texas require inspection?
 
Since there's not really a temp difference I would say the cat is bad.

Emissions testing requirements vary by county in Texas.
 
On Jan 1 this truck will be 24 years old and exempt from emission testing....
Safety items checked only.....that's why all of my toys are 89 and older.....:D

If the inspection station rolls out the old "visual test for emissions items need to be in place".... you're at the wrong shop...most places I go to don't even lift the hood...:thumb:
 
Try this, and I'll bet you a dollar that you'll pass your emission test.

1.) Drive your Blazer until your gas tank is almost completely empty.
2.) Put about 5 gallons of Ethanol (E85) in your tank.
3.) Flip your breather top upside down to allow more air flow into your engine.
4.) Go back to the emission testing facility and have it checked with a warm engine.
5.) After your done passing your emission test, go fill up with normal gas to dilute the E85.

E85 will reduce the Nitrogen Oxide at your tailpipe by more than 90% (see link below and scroll to bottom). E85 will not hurt your gas hose, carb rubber, or anything else no longer than you'll have it in your system. Hell, all gas sold today in major cities has 10% Ethanol in it already. I've been running 10% Ethanol in all my vehicles for a decade now and there's been no rubber deterioration. Do it... It'll work and pass your inspection.

http://www.consumerreports.org/cro/2011/01/the-great-ethanol-debate/index.htm

Also see http://www.afdc.energy.gov/vehicles/flexible_fuel_emissions.html
 
wasted wages said:
On Jan 1 this truck will be 24 years old and exempt from emission testing....
Safety items checked only.....that's why all of my toys are 89 and older.....:D

If the inspection station rolls out the old "visual test for emissions items need to be in place".... you're at the wrong shop...most places I go to don't even lift the hood...:thumb:
Click to expand...


Yeah I know, just gotta get through this last inspection... I really like driving this blazer though so I really want to gets past this inspection.
 
PWagon said:
Try this, and I'll bet you a dollar that you'll pass your emission test.

1.) Drive your Blazer until your gas tank is almost completely empty.
2.) Put about 5 gallons of Ethanol (E85) in your tank.
3.) Flip your breather top upside down to allow more air flow into your engine.
4.) Go back to the emission testing facility and have it checked with a warm engine.
5.) After your done passing your emission test, go fill up with normal gas to dilute the E85.

E85 will reduce the Nitrogen Oxide at your tailpipe by more than 90% (see link below and scroll to bottom). E85 will not hurt your gas hose, carb rubber, or anything else no longer than you'll have it in your system. Hell, all gas sold today in major cities has 10% Ethanol in it already. I've been running 10% Ethanol in all my vehicles for a decade now and there's been no rubber deterioration. Do it... It'll work and pass your inspection.

http://www.consumerreports.org/cro/2011/01/the-great-ethanol-debate/index.htm

Also see http://www.afdc.energy.gov/vehicles/flexible_fuel_emissions.html
Click to expand...


Interesting.... I'll might give this a try if I can find a station... I've got a little over half a tank, so I've got plenty to burn looking for a station though...:D
 
Appreciate everyone's comments... Finally passed the inspection - I replaced the cat! I wanted to go duals anyway so it was a good excuse to do it....
 
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