I am not a smog expert but it is my understanding that
the heat of combustion is high enough to make the cat
reaction work.   I think your mechanic is wrong in his
explanation but he could be right about replacing the
part or he could just be desperate.   There are two
types of cat failure I am certain about.   One is the
obvious sound that it makes when the ceramics get
busted up and it sounds like bees buzzing in the
basket.   The other is the silent death of two much
hydrocarbon because you unplugged your o2 sensor, have
a crack in your exhaust or have crapped it up with too
much lead.   If your mechanic knows these things
perhaps he has made a good choice.   On the other hand
if you have in excess of 100k, you plan on keeping the
van and you want to spare the air, even if you do not
need a new cat it is a good investment, but you may
want to continue to look elseware for the problem.
         gary

Date:    Fri, 23 Aug 2002 08:23:27 -0700
From:    van man <vannman99@YAHOO.COM>
Subject: Bad Cat = No Smog?

Hi,

My mechanic thinks my van wont pass smog because the
cat isnt getting hot enough(meow, purr), therefore I
need a new cat.

These numbers dont mean much to me:

IDLE 0.17% CO 135PPM HC
2500 0.35      90PPM
Before CAT at IDLE 3.65% CO 290PPM HC.

I have already order the new cat and will replace it
tomorrow, but was wondering what you smog pros thought
about this diagnosis.  I guess they used some kind of
infared something or other to tell if the cat was
getting hot enough...

Thanks,

Jeff

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