If the vehicle is marginal already, yes the effect could become enough to
push you over the edge.  Personally I always keep my vehicles in the range
where I don�t worry about being close to the edge.  If you are close enough
for it to have an effect, you need to look at the major causes of nox
failure. Cat converter and timing and air leaks causing lean burn.
jimt

On 9/9/05 1:05 PM, "Doug in Calif" <vanagon@astound.net> wrote:

> Jim, not to disagree with you, but your comment leaves me wondering why my
> mechanic who has had a local shop here in the bay area for over 30 years and
> he has been doing and still does smog for somewhat exclusively German cars,
> told me specifically that you want to get it checked on a cold morning vs.
> hot afternoon to get the NOx as low as possible.  Could it be a minimal but
> perhaps readable effect?
> 
> Doug