Date: Fri, 16 Jul 1999 00:51:53 -0700
Reply-To: Coby Smolens <cobys@WELL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Coby Smolens <cobys@WELL.COM>
Subject: Re: Gas versis catalytic converter
In-Reply-To: <613845B3BA2BD111B80A00805F19A12B02EA70E1@xch-sbc-03.co.bna.boeing.com>
Content-Type: text/plain; charset="iso-8859-1"
I was under the impression that the difference between California and the
rest of the country effectively disappeared in half-year '83, and that all
states (except maybe Alaska and Hawaii?) used the Cat thenceforward... No?
First things first. What happens to the Cat is dependent on what goes into
it, and on the temperature of the exhaust. So what exactly is happening to
yours? Is it coming apart, melting down, contamination, blockage - what?
Breaking up is not so very hard to do - if it's a cheap Cat. I've seen PFP
converters come apart in the time frame you're talking about, in otherwise
perfectly running vans.
Meltdown comes from overheating - duh. Excessively rich mixture or leaky
exhaust valves could do this - a little too much fuel getting into the Cat.
An excessively lean mixture could do the same. So could chronically poor
combustion due to a number of reasons. Contamination or blockage could also
be caused by excessive fuel in the mix, or chronic misfiring.
The best diagnosis is checking the exhaust gas content before and after the
Cat, coupled with temperature readings of the exhaust ahead of, at, and
after the Cat.
There should be less than 100 ppm HC at around .4-.7% CO ahead of the
converter (on very clean running, relatively new engines, this reading could
be very low - say 20 - 50 ppm HC) and almost nothing after it. The cat temp
should be 500-600 degrees F. at 2500 rpm, a marked increase over the exhaust
system before and after it, as much as 100-200 degrees F. difference. If you
make these measurements and get numbers significantly in variance with these
readings, your next job is to figure out why, cause it is your engine, not
so curiously, that is killing the Cat.
Coby
Valley Wagonworks
"Intimately acquainted with VW Vans since 1959"
Volkswagen Bus, Vanagon, Westfalia and Eurovan
Repair and Service Specialists
1535 Sir Francis Drake Blvd., San Anselmo, CA 94933
Voice:(415) 457-5628
Fax: (415) 457-0967
http://wagonworks.com
mailto:contact@wagonworks.com
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM]On Behalf
> Of Greenamyer, William L
> Sent: Thursday, July 15, 1999 6:37 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Gas versis catalytic converter
>
>
> I have a 1984 Vanagon Waterboxer that seems to be eating catalytic
> converters in less than a year. I have been told several
> different stories
> about what could be the problem. Injector pattern not right, wrong mix,
> air-fuel ratio wrong, etc but most of this should manifest itself in some
> other symptom. The latest from a mechanic is that I should be
> using premium
> gas in the van (octane 92) rather than octane 87. I am just at a
> loss right
> now. The van gets 20MPG which includes some distance going up a 6 degree
> grade with the air conditioning on and the still being able to
> acclerate on
> the freeway going 70 MPH. The 1900 engine has been replaced with a 2100
> (two years and many miles ago). I am looking for inputs as to
> what could be
> the real problem. Also, at idle, the engine seeks a lot of the time. By
> that I mean it revs up a little and then settles back down to normal.
>
> William
>
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