I just went through the same thing on my father's 95 3.9 with almost the
same exact readings. The O2 sensor was faulty causing it to run lean (hot
combustion chamber) which makes for high NOx. We also cleaned out the EGR
for good measure.
----- Original Message -----
From: "Eric Hufstedler" <mopar@ehuffy.com>
To: <dakota-truck@dakota-truck.net>
Sent: Wednesday, August 18, 2004 10:07 AM
Subject: DML: smog info
>
> Whoops. I left out the subject on that last one...
>
> A friend failed the california smog test on his 95 dakota 318 auto.
> (high HC and NO at 15 mph, high but passing at 25mph also).
>
> In looking up info on it, i found this site which seems pretty useful if
> you're not very familiar with smog checks:
>
>
http://www.smogcheck.ca.gov/StdPage.asp?Body=/Geninfo/OtherInfo/Vehicle_Inspection_Report_Glossary-May_1996.htm#EGR
>
> Here are the actual numbers:
>
> MPH HC CO NO
> 15 92 (88) .33 (.64) 847 (508)
> 25 53 (53) .15 (.78) 491 (761)
>
> #'s in () are max allowed.
>
> His cat does make a lot of noise (which when mine did the same, was
> replaced under warranty). On mine (99 dak), it was some baffle inside. I
> don't know if that affects performance or not.
>
> He's also missing on at least one cylinder, so the HCs will probably be ok
> when he replaces the wires (which he said were in fact bad when he checked
> them, even though they are only 6 months old..)
>
> His only dilemma (at the moment) is whether to replace the cat now or not.
>
> Can any of you smog experts tell from the emission if the NO is cat
> related, or EGR, etc?
>
> thanks,
> eric
>
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