Emissions- what goes wrong...

["estorhok" <estorhok@domain.elided>]

Its always interesting for me to read about emissions issues- being that is
what I do for a living.  And I've enjoyed reading Pat Braden's look of the
Bosch EFI system...

Anyway- if your favorite Alfa doesn't pass emissions checks, more than
likely, your catalyst has died.  Number 2 on the list- likely the O2 sensor.
Of course this isn't what you wanted to hear- the cat is pretty much the
most expensive single part on the car...

I guess a better answer is why they fail.  Mostly 2 ways- overheating and
poisoning.  For an Alfa, both seem likely.  The overheating typically comes
from a misfiring car- think about it, you just pass a blob of air and fuel
with enough energy to move your car, which generates lots of heat in the
cat.  So if you still have live catalysts on your car, keep an eye on
misfires.  I worry about this on our 164, but we don't have checks here in
MI (yet).  Oh, this could cause a performance problem- the dreaded melted
cat- if the temp gets high enough, the ceramic substrate will actually
melt....

How does it get poisoned?  Since unleaded fuel, the most common poison is
engine oil.  The metallic additives, like phosphorus (sp?) coats the active
sites on the cat very much like lead did.  Again, I worry about this on our
164, since I've seen so much oil in the intake at one time.

On a side note- well not so side- one of the most amusing posts I've ever
seen when surfing the net was on the rec.auto.sport.tech news group, where
one person declared "catalysts have no impact on emissions"  since he
managed to pass the test with no cats.  Well, cats do about 95% of the work
on a new car, and if you can pass with dead or no cats, then your states
emission tests is VERY easy.  Some of the limit numbers I hear about are
what engines put out, and for us OEMs, the EPA limits are about 95-97% more
strict.

Eric Storhok
Ann Arbor, MI
first note since moving to outlook- I hope this makes it ok...

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