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Discussion Starter #1
I recently took my B11 sentra into to be smogged. The sentra failed the test as their were too many unburnt hydrocarbons in the exhaust. The smog technician suggested that the EGR vacuum control could be the problem. After arranging the vacuum lines to the vacuum line diagram under the hose (same as image below) I found that the control vacuum hose for the EGR valve has no vacuum in it at any rpm or engine temperature.

I am curious on how I show proceed to get the car smog worthy. I am thinking that I might have to replace one of the Thermal Vacuum Valves or the Vacuum Canister, but has anyone else had this sort of problem.

For further reference the car otherwise runs fine, I have noticed no idle problems or anything else related to a faulty EGR.

 

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Discussion Starter #2 (Edited)
Update

Just today I had the car smogged again and it is producing far too many unburnt hydrocarbons (over twice legal limit). Also, the EGR valve still has no control vacuum to it. However, when control vacuum was manually applied to the EGR valve by a pump, the engine sputtered while idling. When there is no control vacuum the car idles and runs fine.
 

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Discussion Starter #4 (Edited)
I know it is not the cat because while my car failed hydrocarbons, it passed the CO test fine. Also, since I live in a smaller city in California, the smog shop didn't test for NOx. Therefore I think it is the problem is with one of the engine mechanisms dealing with recirculating unburnt fuel from the exhaust.

I was under the impression that the EGR valve was pivotal in taking fumes from the exhaust manifold and recirculating them into the intake. How does the EGR valve affect NOx?

EDIT:
Also, to anyone who might have experience with this, in order to pass I also need new tubing for the PCV valve. Because it is of such unique design, I don't know where to find a cheaper alternative to going to the dealership.
 

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I know it is not the cat because while my car failed hydrocarbons, it passed the CO test fine. Also, since I live in a smaller city in California, the smog shop didn't test for NOx. Therefore I think it is the problem is with one of the engine mechanisms dealing with recirculating unburnt fuel from the exhaust.

I was under the impression that the EGR valve was pivotal in taking fumes from the exhaust manifold and recirculating them into the intake. How does the EGR valve affect NOx?

EDIT:
Also, to anyone who might have experience with this, in order to pass I also need new tubing for the PCV valve. Because it is of such unique design, I don't know where to find a cheaper alternative to going to the dealership.


The egr recirculates burnt exhaust gases back into the intake to reduce combustion temperatures therfore reducing NOx. From what I understand NOx is formed when the oxygen and nitrogen in the air are subject to high temperature such as in the combustion chamber, reducing the temperature reduces this formation.

EGR VALVE

I would also check the exhaust gas sensor,airfilter, and ignition system.
 
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