That is perfectly normal. NOx is formed by the combination of combustion
temperatures and pressure and excess O2. Yes too lean creates more NOx. That
is why the O2 sensor is needed to maintain at control over mixture. That is
why the dyno test is needed to test for it. You don't get Nox at idle.  You
need a Cat.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
David McSparron
Sent: Wednesday, June 17, 2009 6:11 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Emissions failure Nox (update)

Latest from the shop that has the van. They put a sensor in before the cat
and found that the Nox is ok at idle but goes high under load. He seems to
think this indicates it may not be the cat.

-Savid ('87 Vanagon 2.1L)