# FAILED smog



## altima93 (Dec 18, 2004)

Hello. I recently FAILED smog and was told by a mechanic that I needed to change the 02 sensor and catalic converter to maybe have it pass.

The car is a 1993 Altima, it has 194,000 miles on it. I was told by another person to change the 02 sensor first and see if it would pass this way first.

He said if that didnt work then change the catalic converter,he was the guy that was selling me the catalic converter. Whats does anyone think ?

Asm emission test results readings for the FAILED smog:
NO(PPM) Max: 704 AVG: 150 MEASUREMENT: 803

Shouls I only change the fron 02 Sensor or both. I want to try this first then as a last resort the catalic converter. Thanks you for your time.

David


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## lshadoff (Nov 26, 2002)

altima93 said:


> Asm emission test results readings for the FAILED smog:
> NO(PPM) Max: 704 AVG: 150 MEASUREMENT: 803
> 
> Shouls I only change the fron 02 Sensor or both.


Neither. High NOX is due to a bad EGR system. It is likely, at your mileage, that the EGR tube is plugged and the system is not working.

Lew


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## altima93 (Dec 18, 2004)

Lew Thanks.

Whats does it it all mean:bad EGR system, EGR tube is plugged and the system is not working.What can I do to try and fix it. Thanks again.


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## lshadoff (Nov 26, 2002)

altima93 said:


> Lew Thanks.
> 
> Whats does it it all mean:bad EGR system, EGR tube is plugged and the system is not working.What can I do to try and fix it. Thanks again.


There is a tube that goes form the exhaust manifold to the EGR solenoid. This tube gets plugged over time. You can try to clean it, but the deposits are hard to remove and the hole is very small. Or, you can buy a new tube and replace it. Also, check the hoses attached to the EGR solenoid for cracks/detached hoses. 

Lew


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## altima93 (Dec 18, 2004)

Lew
Again Thank You.


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## lshadoff (Nov 26, 2002)

altima93 said:


> Lew
> Again Thank You.


Nolol problemo  

Also, check the timing, and set it at the low end of the recommended setting. Advanced timing makes for higher NOX.

Lew


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## KA24Tech (Feb 2, 2004)

Ishadoff is correct that typically high NOX is associated with the EGR system. I do recommend a new O2 sensor mainly due to time and mileage, however, the first place I would start to clean is in the EGR valve itself on top of the intake manifold. I would also clean out the passages in the manifold. You will just need to buy a new gasket for the valve. Generally I would clean the throttle body and IAC solenoid but start with the EGR cleaning. I do not think that you have a real problem with your catalytic converter simply because the HC and CO weren't high. 

Troy


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## Asleep (Jan 19, 2003)

yeah like lew said, check the timing too. when i failed emissions, my timing was retarded 3 degrees... dont know how or when that happened but it made me fail twice...


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