RE: Emissions

[Chris Coracini <Coracin@usdl.com>]

>
>
>>  Finally passed the 88 16V!Test limits:  HC@220pp,   CO at 1.20Pct
>> First:        251ppm    2.15PctSecond    233ppm    1.98Pct (changed
>> plugs, cap, rotor)Finally:    131 ppm    .18Pct (after they leaned it
>> out) Still have whitish/gray smoke from tail pipe.   Any ideas?
>
>How did they "lean it out?"
>
>If your controller and oxygen sensor are working properly
>there is no adjustment required to lean it out. 

not true during idle, you can adjust the CO with a 3mm allen tool.

> The normal
>output should be about 100 ppm HC and 0.8% CO
>_without_ a catalyst.  In the presence of a decent working
>catalyst you should see less than 20 ppm HC and 0.1% CO.

this is true, mine passed (3 years ago) with about what you wrote.  the
limit was about 300ppm?  and i got 20ppm!  the guy was shocked (so was
i).
>
>I suspect they "leaned it out" be over adjusting the idle
>air mixture (hex head screw in air flow meter) to limit
>the fuel flow at idle despite what the controller was trying
>to do based on a bad O2 sensor.  This will work for
>passing an idle test, but makes the mixture too lean in
>some cases.  This is not a good thing to do.

16V's have an idle switch that switches the FI into open-loop (no O2
sensor feedback) during idle.  this allows you to adjust the mixture
using the 3mm tool.  when you do adjust the idle, the O2 sensor isn't
going to do a thing to change it.  during normal operation, neither
throttle switch is closed and the system runs closed-loop.  this is when
the O2 will control the mixture at 14.7:1 no matter what the CO is set
for (unless it's WAY outta wack and the O2 cannot compensate for it, but
then it would barely run anyway).  other open-loop situation is during
WOT for full-load enrichment.

chris
86 16V scirocco

>

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