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Discussion Starter · #1 ·
Help! I just failed an emissions test in Rhode Island. Hydrocarbons and Carbon Monoxide are fine! Oxides of Nitrogen (Nox) are not. 4.05gpm actual versus allowed 3.20gpm
1987 Buick GN, stock chip, stock injectors, stock turbo, recent valve job. K&N conical intake, Poston High flow Catalytic converter, adjustable fuel reg set at 35psi
Car runs smooth, great. Idle seeks a bit in open loop. Where do I look?
 

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Here is what I found:

OXIDES OF NITROGEN (NOX)

Nitrogen makes up about 78% of the air we breathe. Though normally inert and not directly involved in the combustion process, combustion temperatures above 2500 degrees F cause nitrogen and oxygen to combine and form various compounds called "oxides of nitrogen," which is abbreviated NOX. This mostly occurs when the engine is under load and the throttle is open wide.

NOX is a nasty pollutant both directly and indirectly. In concentrations as small as a few parts per million, it can cause eye, nose and lung irritations, headaches and irritability. Higher concentrations can cause bronchitis and aggravate other lung disorders. Once in the atmosphere, it reacts with oxygen to form ozone (which is also toxic to breathe) and smog.

To reduce the formation of NOX, Exhaust Gas Recirculation (EGR) is used. By recirculating a small amount of exhaust gas back into the intake manifold to dilute the air/fuel mixture, EGR has a "cooling" effect on combustion, thus keeping temperatures below the NOX formation threshold.

On 1981 and later engines with computerized engine controls, a special "three-way" catalytic converter is used to reduce NOX in the exhaust. The first chamber of the converter contains a special "reduction" catalyst that breaks NOX down into oxygen and nitrogen. The second chamber contains the "oxidation" catalyst that reburns CO and HC.

High NOX emissions are almost always due to a defective EGR valve (or some component that controls the operation of the EGR valve). A related symptom that usually occurs when EGR is lost is spark knock (detonation) during acceleration.

Now go answer my question.
 

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Discussion Starter · #3 ·
Salvage 6,

Very helpful with the Nox explanation....Thanks!

I have tested the EGR valve with a tester,(Results ok) and have a new EGR Valve solenoid. How do I know it is doing its job from there? Also, I have a couple of "Open" vacuum lines in the system, and have no idea where they go? I could use a good detailed vacuum diagram for the 87 Turbo???? Any Ideas?

Is it possible, the Poston "High flow" converter is not doing its job?
Originally posted by Oldsmobuick:
Help! I just failed an emissions test in Rhode Island. Hydrocarbons and Carbon Monoxide are fine! Oxides of Nitrogen (Nox) are not. 4.05gpm actual versus allowed 3.20gpm
1987 Buick GN, stock chip, stock injectors, stock turbo, recent valve job. K&N conical intake, Poston High flow Catalytic converter, adjustable fuel reg set at 35psi
Car runs smooth, great. Idle seeks a bit in open loop. Where do I look?
 

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Not much to add here, except to say I passed with a Poston's cat. Prolly a good idea to go to the other board if you don't get help here, and post in detail what lines are involved.
 

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Discussion Starter · #6 ·
What other board?

Remember, I'm a virgin on this site!

Originally posted by Turbo_Tim:
Not much to add here, except to say I passed with a Poston's cat. Prolly a good idea to go to the other board if you don't get help here, and post in detail what lines are involved.
 

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turbobuick.com

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Jim: 87 GN with: TA-49/PTE .63 housing; stock motor, transmission and converter; MSD 50#; CAS V-4; 3" DP; ATR 2.5" SS exhaust; 62 mm Hemco; Translator w/3" MAF; Bigmouth air system; SMC alcohol; Walbro 340; BFG DRs; and Extender 100 chip with 21* timing. Best ET/mph with w/93 octane + alcohol were 11.961/117.05.
 

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For stock Buick vacuum lines I would suggest the Buick Service Manual.

Maybe there's a diagram at gnttype.org

I am not sure worth a check there first.

I also doubt it's the cat.
 
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