Yes, vacuum leaks most definitely cause high NOx
readings; but you would think they also would cause
problems with HC due to lean misfires. The most likely
cause is the EGR system is not working as EGR cools
down cylinder temps, and high cylinder temperature is
what causes NOx. Other things to look for are too
advanced timing, carbon build-up in the cylinders or
improper valve timing which can cause high cylinder
pressures, a bad converter, or high coolant
temperature.
- kenneth parker <elkeni@mac.com> wrote:
> Would a vacuum leak affect the NOx reading? If so,
> I would have a
> good look and listen to all hoses and the boot. I
> have no idea if a
> leak would affect the readings, but if so, check the
> connections and
> hoses out.
> Ken
> On Sep 5, 2005, at 7:13 PM, Otis Keith wrote:
>
> > Brad,
> > If you cannot find the problem and need it to
> pass, try adding
> > about two to three pints of alcohol to about 1/4
> tank of gas. Drive
> > around about 5 min before the next test and that
> should do it. This
> > is not a cure, just a slick way to pass the test
> until you can resolve
> > the issue.
> > Otis
> > St. Louis, Mo.
> > 86 505 sti
> > 86 505 Turbo SW
> > 85 505 SW
> > 81 505 TD
> > 81 504 Diesel SW
> >
> > tilac1 <tilac1@yahoo.com> wrote:
> > My '87 XN6 505 wagon just failed the dyno/cruise
> portion of the
> > emmisions inpection here in MA. Maybe some other
> owners can give
> > suggestions on what to do. The HC and CO are
> within spec but the NOx
> > is 4.13, the limit is 3.00.
> >
> > Car runs super, cat converter is a year old, O2
> sensor is new as are
> > plugs, cap and wires. Ignition timing is to spec
> also.
> >
> > Besides changing the oil, getting out on the
> highway, and adding some
> > Techron, what else can I do before going back for
> a retest in hopes of
> > passing?
> >
> > PS I don't want to monkey with the mixture.
> >
> > Thanks,
> >
> > Brad in MA
> > '87 Liberte 200K miles
> >
> > [Non-text portions of this message have been
> removed]
> >
> >
> >
> >
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Received on Mon Sep 5 23:31:40 2005
