To high Nox

[Rod L Davis]

I don't know but some new OBDII systems require this because of losses
and or leaning richening due to dissimilar metals creating a voltage.
maybe your system was leaning out to far causing nox.
Rod


John T. Luyster wrote:
> 
> Thanks. Fairly enexpensive to do.  I'll try it!  What is an acceptable loss?
> Microvolts?
> 
> Rod L Davis wrote:
> 
> > Try a ground wire to both exhausts around O2 sensors.
> >
> > John T. Luyster wrote:
> > >
> > > I have a 1999 Infinity QX4 that I'm trying to get a set of headers
> > > emission legal (Smog Exempt) in California.  My first test failed
> > > because of high Nox.  This is determined by a formula they come up with
> > > that extends the results out to at least 50K at which point my Nox
> > > exceeded that limit.  (It would pass a standard street smog test no
> > > problem)  After some investigation I found an Infinity Service Bulletin
> > > that suggested adding a ground wire from the intake manifold to the
> > > righthand cylinder head.  Further diagnostics revealved a lazy or slow
> > > O2 sensor at which time I replaced all four.  After this I had the
> > > vehicle sniffed to verify any changes.  The Nox was down substantially.
> > > At this time I set all the SRT's and drove approx. 50 miles to make sure
> > >
> > > no DTC's popped up.  Off to the test lab again and failed again with
> > > high Nox.  This vehilce has no mods done to it.  Factory ECU. The only
> > > thing I can think of might cause this high Nox would be the design or
> > > flow of the tube off the header to the EGR on the engine.  Any ideas????
> > >
> > > JT