[20v] Lowering Emissions 90Q 20V

[Brett Dikeman]

At 3:25 PM -0700 10/25/02, james accordino wrote:
>That makes perfect sense.  From my limited chemistry
>knowledge.  Two things initiate or speed up
>chemical/catalytic actions/reactions.  Heat and a
>catalyst.  I guess that's why they're called
>"catalytic converters"?  Really good point though.

Keep in mind that part of the lambda control system's function is to
manage the catalytic converter- they're NOT supposed to get "perfect
mixture" all the time.

If the O2 sensor is slow to respond, or there's something wrong
elsewhere(such as ignition problems dumping some unburned fuel, etc),
the converter won't be at optimal temp.  Same thing goes for things
like the temperature sensor for the ECU...

I don't recommend "replace O2 sensor if you fail emissions", but I
would recommend religious replacement every 60k(Audi says replace on
the 20vt if they are over 50k and the car isn't performing right),
and good maintenance with regards to the "consumables."

If mileage, starting performance, power, etc all seem down, you have
a lot of miles on the car, everything else checks out(including the
catalytic converter), and emissions are still out of whack...don't
rule out clogged injectors.  Sometimes it is beyond the reach of a
bottle of fuel injector cleaner- dirt and really hard deposits just
aren't going to be taken care of by anything except ultrasonic
cleaning/backflushing.  Best preventative maintenance there is
regular fuel filter changes, and periodic use of injector cleaner,
but nothing is guaranteed.  It is a shame injectors aren't more
DIY-er friendly as far as servicing and evaluation; the are
incredibly simple devices.

Everyone I've talked to who has sent out injectors for servicing has
had goods things to say- better starting, better throttle response,
that sort of thing.  Expensive($20-25 per), but usually the cost of
servicing an entire set is far less in comparison to the cost of even
one new injector.

Brett
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