Technical aspects of automobiles

Checking a catalytic converter

How can one determine if there is a problem with a catalytic converter?

The specifics that lead me to this question are:

We have a recently acquired 1988 Olds 88 with 3.8L EFI in which the
mileage is lower than seems reasonable (19 mpg in long distance driving
in overdrive on the Interstate – friends with similar vehicles report
mid-20′s).  Also, I’ve noticed that the exhaust has a peculiar odor –
not unburned gas exactly, but obviously a hydrocarbon of some sort.
The odor is frequently noted after driving for several miles as we get
out of the car.  We have also noticed it faintly in the car on stopping
at traffic lights on a few occasions (presumably from the outside
ventilation intakes).

The engine appears to be in excellent condition (starts and performs
well) but there is some soot visible in the tail-pipe.  All spark plugs
are in good condition and were of normal appearance when removed for
examination.  A external examination of the exhaust system revealed no
readily apparent leaks or damaged components.

One friend mentioned that he had heard of catalytic converters becoming
"plugged" with a resultant increase in emissions and in backpressure
(with loss of mileage).  The problem is supposedly more apparent after
driving a distance and the catalyst has heated up.  Has anyone had any
experience of this sort?  Given that this is possible, I’ve considered
the hypothesis that the pressure in the exhaust system between the
manifold and converter is sufficient to blow past a seal and leak
exhaust in the engine compartment.  Comments?

—————————————————————————–
Keith Pyle                                UUCP: …!cs.utexas.edu!execu!keith
Execucom Systems Corp., Austin, Texas     Internet: ke…@execu.com
"It’s 10 o’clock.  Do you know where      Disclaimer: Everything I say is
   your child processes are?"               true unless I use the word ‘the’.
—————————————————————————–

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posted by admin in Uncategorized and have Comment (1)

One Response to “Checking a catalytic converter”

  1. admin says:

    In article <30…@sequoia.execu.com> ke…@sequoia.execu.com (Keith Pyle) writes:

    %How can one determine if there is a problem with a catalytic converter?
    %
    %The specifics that lead me to this question are:
    %
    %We have a recently acquired 1988 Olds 88 with 3.8L EFI in which the
    %mileage is lower than seems reasonable (19 mpg in long distance driving
    %in overdrive on the Interstate – friends with similar vehicles report
    %mid-20′s).  Also, I’ve noticed that the exhaust has a peculiar odor –
    %not unburned gas exactly, but obviously a hydrocarbon of some sort.
    %The odor is frequently noted after driving for several miles as we get
    %out of the car.  We have also noticed it faintly in the car on stopping
    %at traffic lights on a few occasions (presumably from the outside
    %ventilation intakes).
    %
    %The engine appears to be in excellent condition (starts and performs
    %well) but there is some soot visible in the tail-pipe.  All spark plugs
    %are in good condition and were of normal appearance when removed for
    %examination.  A external examination of the exhaust system revealed no
    %readily apparent leaks or damaged components.
    %
    %One friend mentioned that he had heard of catalytic converters becoming
    %"plugged" with a resultant increase in emissions and in backpressure
    %(with loss of mileage).  The problem is supposedly more apparent after
    %driving a distance and the catalyst has heated up.  Has anyone had any
    %experience of this sort?  Given that this is possible, I’ve considered
    %the hypothesis that the pressure in the exhaust system between the
    %manifold and converter is sufficient to blow past a seal and leak
    %exhaust in the engine compartment.  Comments?
    %–
    I have a Mazda pickup which has shown the same things happening.  I
    took it into a Mazda dealer and they told me the convertor was
    plugged.  It sounds like you have the same problem.

    I would take it to a dealer to check it (if you trust them to be
    reasonable).  It may be under warranty.  If not, you should be able
    to get a used one at a wrecking yard and have someone install it for
    you.

    Thanks                  #  Sometimes all it takes to make someone
            Bill            #  a real motorcycle enthusiast is…
    DoD#092                 #  one ride.

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