Re: '87 5000s fails emissions test

[Edward Armstrong <armstron@crl.com>]

``

On Sat, 25 Feb 1995 AUDIDUDI@delphi.com wrote:

> My '87 5000s failed the new, more stringent Arizona emission test yesterday
> and I need some advice as to what might need "fixing" otherwise I will have
> to take it to a shop and [gasp!] pay someone else to fix it for me...
> 
> Both the HC (.82gm/mile) and CO (5.6gm/mile) were well within spec; only the
> NOx reading was too high (6.8gm/mile v. a limit of 3gm/mile).  In the past 4
> months, I've replaced the plugs, plug wires, cap & rotor, O2 sensor, cat and
> air & fuel filters; I also readjusted the FI mixture and advanced the timing
> by 6 degrees. The car runs better than it has in 2 years and gets better gas
> mileage to boot but unless I can get it to pass emissions...
> 
> Other than resetting the timing to factory specs, I don't know what else to
> try.  I know how to deal with HC and CO but have no experience dealing with
> NOx and since I only have one free retest (after that, they're $16.75 per!),
> I want to "round up the usual suspects" before trying again.  Help!
> 
.... High NOx is an indication that the mixture is too lean and/or the
cat converter is shot. Since you already are below CO2 and HC spec you
might get away with a _slight_ enrichment. 
  -ed