how do I know if my catalytic converter has failed?

An automobile's catalytic converter uses a catalyst to convert harmful exhaust fumes into harmless ones. Find out what happens when your catalytic converter stops working properly -- and how you can tell -- in this episode.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brainstuff from house stuff works dot com where
smart happens. Hi. I'm Marshall Brain with today's question, how
do I know if my catalytic converter is failed? To
understand why a catalytic converter fails, you need to know

(00:22):
how it works. The catalytic converter is the part of
the automobile exhaust system that converts harmful compounds in the
exhaust into harmless compounds. It does this by using a catalyst,
which speeds up chemical reactions. The catalysts can take unburned
hydrocarbons in the exhaust stream and burn them. It can
turn carbon monoxide into carbon dioxide, and so on. The

(00:46):
thing that does this is a honeycomb piece of ceramic
with the catalysts embedded in it. And if you were
to ever look at this, the holes going through that
catalysts are very very small. So one of the easiest
way is for a catalytic converter to fail is for
it to become clogged. Often, the only way to tell
if your catalytic converter is plugged up is to remove

(01:08):
it and check for the change in engine performance, or
some mechanics temporarily remove the oxygen sensor from the exhaust
pipe ahead of the catalytic converter and see if that helps.
It opens up a big enough hole to lead exhaust
through if the converter is plugged up. Sometimes you can
tell that a converter is clogged because you don't go
any faster when you push on the gas pedal at

(01:30):
a certain point. Also, there's usually a noticeable dropping gas
mileage associated with a clogged converter. A partially clogged converter
often acts like an engine governor. A totally clogged converter
causes the engine to quit after a few minutes because
of all the increased exhaust back pressure. A catalytic converter
can also fail because of bad exhaust valves on the

(01:53):
engine or fouled plugs, which cause unburned fuel to overheat
the converter. A catalytic convert to relies on receiving the
proper mix of exhaust gases at the proper temperature. Any
additives or malfunctions that cause the mixture or the temperature
of the exhaust gases to change reduce the effectiveness and

(02:13):
the life of a catalytic converter. Letted gasoline and overuse
of Certain fuel additives can also shorten the life of
a catalytic converter by poisoning the catalyst. Here's a safety reminder,
do not park your car over tall grass or piles
of dry leaves. Your cars perfectly running catalytic converter gets

(02:34):
incredibly hot, hot enough to start fires. Do you have
any ideas or suggestions for this podcast? If so, please
send me an email at podcast at how stuff works
dot com. For more on this and thousands of other topics,
go to how stuff works dot com and be sure
to check out the brain stuff blog on the house
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