There are two ways a converter can fail:
- It can become clogged.
- It can become poisoned.
There really is no "inspection port" for the consumer or mechanic to
see an actual clog in a converter. Often, the only way to tell if a
catalytic converter is malfunctioning (plugged) is to remove it and
check the change in engine performance. When a clogged converter is
suspected, some mechanics temporarily remove the O2 sensor
exhaust pipe ahead of the catalytic converter and look for a change in
A catalytic converter 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 life of the catalytic converter. Leaded
gasoline and the over-use of certain fuel additives can shorten the
life of a catalytic converter.
A catalytic converter can also fail because of:
- Bad exhaust valves on the engine
- Fouled plugs causing unburned fuel to overheat the converter
Sometimes you can tell that a converter is clogged because you
don't go any faster when you push the gas pedal. Also, there usually is
a noticeable drop in gas mileage
associated with a clogged catalytic
converter. A partially clogged converter often acts like an engine
governor, limiting the actual RPMs to a fast idle. A totally clogged
converter causes the engine to quit after a few minutes because of all
the increased exhaust back pressure.
The catalytic converter, like the rest of the emissions system,
typically has a warranty length that exceeds the term of the warranty
for the rest of a typical U.S. automobile.
Here is a safety reminder: Do not park your car
over tall grass or
piles of dry leaves. Your car's perfectly running catalytic converter
gets very hot -- enough to start fires
! You can keep it running well by
keeping the ignition system
in top shape, to prevent any unburnt fuel
from entering the catalytic converter.