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| How
do I know if my catalytic converter is defective? |
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| Catalytic
converters are defective when they become clogged or poisoned. You
may sometimes be able to feel when a converter is partially clogged,
or defective, when you do not go any faster when you step on the throttle.
This may also be accompanied with a noticeable drop in gas mileage.
A clogged converter will cause increased backpressure in the exhaust
system. This increased backpressure prevents the engine from breathing
properly which in turn may cause the engine to quit after a few minutes
of driving or feel like an engine governor limiting the RPM's the
engine can achieve. You may actually hear a whistling or choking sound
when applying the throttle. |
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A
catalyst that has broken apart internally and is loose in the system
or has worked its way back to the muffler can also cause rattling
noises. This rattling may be prevalent at idle but go away as speed
is increased. Sometimes you may tap on the converter with a rubber
mallet and hear the core rattling. If you discover any of the above
your converter needs to be replaced.
Since
there is no inspection port for you to see if you have an actual clog
in a converter there a couple things you may try to help diagnose
a defective converter. Many mechanics will remove the oxygen sensor
and look for a change in the vehicles performance. If a performance
change is noted, your converter needs to be replaced. You must be
extremely careful if you run the engine with the oxygen sensor removed
since there is a risk of fire and asphyxiation caused by escaping
engine exhaust and exhaust gases.
A vacuum gauge that also has a fuel pressure gauge, or a pressure
gauge that has a 1 to 10 pound scale, may also assist you in diagnosing
a clogged exhaust. |
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If you connect the gauge upstream of the converter, either in an emission
test port or by fashioning an adapter in the oxygen sensor hole, you
can measure the exhaust backpressure. A general rule of thumb is no
more than 1.5 pounds of backpressure. Another test, using a vacuum
gauge, is to measure the engine vacuum at curb idle and at 1600 RPM.
If engine vacuum is 21 inches at curb idle and 15 inches at 1600 RPM
then there is a good possibility your catalytic converter needs to
be replaced. |
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| You
may also take the converter off the vehicle and check it for damage
or clogging. Shining a flashlight into the core of a honeycomb style
converter will reveal whether the honeycomb is partially clogged,
damaged, or loose from the edges. |
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| Finally,
a converter can be defective because it has become poisoned. When
a catalytic converter becomes poisoned it loses its ability to effectively
control emissions. Some common causes for poisoning and converter
degradation are using leaded fuel, fuel additives containing lead,
an out of tune engine, engine management system failure, faulty engine
sensors, just to name a few. |
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| If
your vehicle is burning an excessive amount of fuel or misfiring,
due to some of the reasons above, it is just a matter of time before
converter failure. A constant rotten egg smell emitting from the tailpipe
is a sure sign of the impending failure of your converter. |
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| If
you do determine that your catalytic converter is defective, it is
extremely important that you determine the reason for its demise.
Always have your emissions checked on an exhaust gas analyzer after
the new converter is installed to ensure your engine and engine management
systems are operating at their peak efficiency. Failure to find and
repair any fault will result in a premature failure of your new converter.
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