high NOX levels on smog check

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Old 01 Mar 2006, 02:35 am   #1 (permalink)
onehappymadman@yahoo.com
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Default high NOX levels on smog check

My 96 camry passed smog a few months ago, passing with wide margins for
everything except for NOX. While it passed NOX, it was above the
average for NOX. I don't remember the exact value, it was maybe 1/2 of
the maximum allowed value.

What could be causing this? Is this a cause for concern?

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Old 01 Mar 2006, 10:47 am   #2 (permalink)
Daniel
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Default Re: high NOX levels on smog check

I have same "generation" '94.
Checking smog test results, nitrous oxide max was apx. 700 ppm, avg.
apx. 150, and measured results were apx. 50. This was for California.
Would guess that means your reading was half the max. apx. 350 ppm?
That would be 7X my 50 ppm (parts per million) - for the same engine.
Nitrous oxides are created when combustion chamber temperatures pass a
certain threshold, so auto makers devised a way to keep the
temperatures lower than that level. For your car the solution is "EGR"
(exhaust gas recirculation). The EGR system includes a vacuum modulator
to vary the amount of exhaust gas recirculated.
The idea is that by introducing gases already burned into the
combustion chamber, the temperature will be reduced. Since the engine
is calibrated with this factor in mind efficiency is not reduced.
When I replaced the idle air control valve, the factory service manual
included a section for removing and cleaning the throttle body off the
car. Along with calibrating the throttle position sensor, was included
directions to soak in solvent and blow with compressed air, the three
orifices in the throttle body that are uncovered as the butterfly valve
progressively opens. These ports lead to the vacuum modulator for the
EGR valve. When I hit the smallest port with compressed air after
application of solvent, (a tiny pinpoint sized opening) a slug of
brownish-black goop was expelled. So you may have something similar.
Not sure about the '96, but on the '94 the PCV (positive crankcase
ventilation) valve that directs "blowby" gases to the intake, is vented
right behind the butterfly valve, very close to those EGR vacuum
modulator ports.
Also, it is not uncommon for the tube that carries exhaust gases to the
EGR valve to become obstructed with carbon deposits. Obviously if the
flow of exhaust is restricted, the overall operation of that system is
diminished.
What to do?
Things affect each other in subtle ways.
I use the RedLine complete fuel system cleaner continuously. One full
bottle, and then a tiny bit with each fuel fill up. RedLine's web site
has detailed technical information showing graphs of how carbon is
removed from the valve faces over time. RedLine has the distinction of
being free of solvents, plus containing a synthetic upper cylinder
lubricant. BMW apparently approved this single product for use. I
mention this because it survives the combustion process to clean
emission control equipment. For example my oxygen sensor still tests
out just fine, and it could conceivably help clean the EGR exhaust
passageway.
You might want to check out auto-rx.com also, regarding cleaning piston
ring lands to potentially reduce blow by gasses.
The best way to clean the throttle body is by removing and following
all the procedures in the manual. Probably couple hundred dollars at
the dealer, versus doing it yourself where conceivably cost could be
zero, though I replaced the base gasket and coolant, plus purchased a
Kragen $99 5 gal. air compressor.
The EGR exhaust passage can be cleaned with some sort of wire. Seemed
like the best way to access would be to remove the distributor.

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Old 01 Mar 2006, 11:10 am   #3 (permalink)
onehappymadman@yahoo.com
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Default Re: high NOX levels on smog check


Daniel wrote:
> I have same "generation" '94.
> Checking smog test results, nitrous oxide max was apx. 700 ppm, avg.
> apx. 150, and measured results were apx. 50. This was for California.
> Would guess that means your reading was half the max. apx. 350 ppm?
> That would be 7X my 50 ppm (parts per million) - for the same engine.
> Nitrous oxides are created when combustion chamber temperatures pass a
> certain threshold, so auto makers devised a way to keep the
> temperatures lower than that level. For your car the solution is "EGR"
> (exhaust gas recirculation). The EGR system includes a vacuum modulator
> to vary the amount of exhaust gas recirculated.
> The idea is that by introducing gases already burned into the
> combustion chamber, the temperature will be reduced. Since the engine
> is calibrated with this factor in mind efficiency is not reduced.
> When I replaced the idle air control valve, the factory service manual
> included a section for removing and cleaning the throttle body off the
> car. Along with calibrating the throttle position sensor, was included
> directions to soak in solvent and blow with compressed air, the three
> orifices in the throttle body that are uncovered as the butterfly valve
> progressively opens. These ports lead to the vacuum modulator for the
> EGR valve. When I hit the smallest port with compressed air after
> application of solvent, (a tiny pinpoint sized opening) a slug of
> brownish-black goop was expelled. So you may have something similar.
> Not sure about the '96, but on the '94 the PCV (positive crankcase
> ventilation) valve that directs "blowby" gases to the intake, is vented
> right behind the butterfly valve, very close to those EGR vacuum
> modulator ports.
> Also, it is not uncommon for the tube that carries exhaust gases to the
> EGR valve to become obstructed with carbon deposits. Obviously if the
> flow of exhaust is restricted, the overall operation of that system is
> diminished.
> What to do?
> Things affect each other in subtle ways.
> I use the RedLine complete fuel system cleaner continuously. One full
> bottle, and then a tiny bit with each fuel fill up. RedLine's web site
> has detailed technical information showing graphs of how carbon is
> removed from the valve faces over time. RedLine has the distinction of
> being free of solvents, plus containing a synthetic upper cylinder
> lubricant. BMW apparently approved this single product for use. I
> mention this because it survives the combustion process to clean
> emission control equipment. For example my oxygen sensor still tests
> out just fine, and it could conceivably help clean the EGR exhaust
> passageway.
> You might want to check out auto-rx.com also, regarding cleaning piston
> ring lands to potentially reduce blow by gasses.
> The best way to clean the throttle body is by removing and following
> all the procedures in the manual. Probably couple hundred dollars at
> the dealer, versus doing it yourself where conceivably cost could be
> zero, though I replaced the base gasket and coolant, plus purchased a
> Kragen $99 5 gal. air compressor.
> The EGR exhaust passage can be cleaned with some sort of wire. Seemed
> like the best way to access would be to remove the distributor.


Ok, I'll look into this.

I use Red Line fuel treatment every now and then. How much do you mean
by "a tiny bit" with each fuel fill up?

Also, is it best to use Red Line with a full gas tank, or with the tank
only half full? The Red Line says it treats a full tank, then I saw
"10 gal" on the side of the bottle, so I was a bit confused.

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Old 01 Mar 2006, 06:46 pm   #4 (permalink)
johngdole@hotmail.com
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Default Re: high NOX levels on smog check

For a 2000 I think you don't want anything near 3 digits for NOx. High
NOx means your engine combustion temperature is high.

The first thing to check, as said, is the operation of the EGR system.
I can send exerpts of my previous posts on the topic. A free loaner
MityVac vacuum pump from Autozone used on the EGR valve is a good
starting point. Then the cleaning procedure mentioned by Daniel.

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Old 01 Mar 2006, 07:54 pm   #5 (permalink)
johngdole@hotmail.com
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Default Re: high NOX levels on smog check

Wrong car. ULEVs should be in the low tens for NOx ppm. LEV probably
not over 100.

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Old 02 Mar 2006, 09:01 am   #6 (permalink)
Daniel
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Default Re: high NOX levels on smog check

You're supposed to use the amount between the marks on the side of the
bottle at each fill up so one bottle treats one hundred gallons of
fuel. I've gotten to just letting it go "glug, glug" four times at
under one half tank (apx. 10 gallons) or a bit more at quarter tank
remaining. I don't think precision is essential here.

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Old 02 Mar 2006, 09:02 am   #7 (permalink)
Daniel
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Default Re: high NOX levels on smog check

You're supposed to use the amount between the marks on the side of the
bottle at each fill up so one bottle treats one hundred gallons of
fuel. I've gotten to just letting it go "glug, glug" four times at
under one half tank (apx. 10 gallons) or a bit more at quarter tank
remaining. I don't think precision is essential here, but long term use
makes the difference. If you look at their grapsh and charts, can take
10,000 miles for full effect which does improve engine breathing, power
and cleanliness.

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Old 02 Mar 2006, 10:23 am   #8 (permalink)
onehappymadman@yahoo.com
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Default Re: high NOX levels on smog check


Daniel wrote:
> You're supposed to use the amount between the marks on the side of the
> bottle at each fill up so one bottle treats one hundred gallons of
> fuel. I've gotten to just letting it go "glug, glug" four times at
> under one half tank (apx. 10 gallons) or a bit more at quarter tank
> remaining. I don't think precision is essential here, but long term use
> makes the difference. If you look at their grapsh and charts, can take
> 10,000 miles for full effect which does improve engine breathing, power
> and cleanliness.


WHAT!!!? Well thanks for letting me know! I've been using the entire
bottle, every time.

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