Causes of TWC Contamination

Like the oxygen sensor, the most common cause of catalytic converter failure is contamination. Examples of converter contaminants include:

• Overly rich air/fuel mixtures will cause the converter to overheat causing substrate meltdown.

• Leaded fuels, even as little as one tank full, may coat the catalyst element and render the converter useless.

• Silicone from sealants (RTV, etc.) or engine coolant that has leaked into the exhaust, may also coat the catalyst and render it useless.

There are other external factors that can cause the converter to degrade and require replacement. Thermal shock occurs when a hot converter is quickly exposed to cold temperature (snow, cold fuel, etc.), causing it to physically distort and eventually disintegrate. Converters that have sustained physical damage (seam cracks, shell puncture, etc.) should also be replaced as necessary.

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