PCV Elbow broken- is this why I failed smog? - JeepForum.com
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Unread 07-23-2013, 02:53 PM   #1
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Join Date: Feb 2012
Location: Phoenix, AZ
Posts: 71
PCV Elbow broken- is this why I failed smog?

Failed smog today for the second time. NOx was too high both times. After the first fail I replaced both O2 sensors, and the NOx numbers went down about 15%. The second time though, the guy noticed that my PCV elbow was snapped off. Could this be why I am failing? My Cat is one year old.

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Unread 07-23-2013, 06:33 PM   #2
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1996 ZJ 
Join Date: Mar 2013
Location: Oakland, CA
Posts: 60
Unlikely, unless you failed the visual for the broken vacuum line.
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Unread 07-23-2013, 11:08 PM   #3
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1993 ZJ 
Join Date: Aug 2010
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High NOx is formed by high combustion temperatures. Usually this is either a lean mixture or misfire/preignition. If your CCV leak was big enough that the PCM couldn't adjust the fuel to compensate it could go lean enough to spike the NOx. It would probably throw a check engine light though. Easy enough to fix the leak and have the test rerun.

If you have worn ignition components that can also contribute to NOx.

Your cat should be scrubbing the NOx though. Make sure to get your Jeep good and hot by driving it for awhile preferably on the highway not stop and start driving for a good ten or fifteen minutes before taking back to get checked. Your cat doesn't work unless it's hot. This especially true if you picked an aftermarket cat that may be more universal, high flow, performance oriented.
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