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Most common causes of internal catalyst failure is due to unburned fuel, lead, phosphorous or engine coolant contamination. These contaminants can begin to clog the catalytic converter and restrict exhaust flow through the system. When this occurs, the back pressure of the exhaust builds up between the exhaust manifold and the converter. Because the exhaust system is not allowed to breathe well, engine stalls, decreased fuel efficiency, lack of acceleration and overall engine performance are compromised.
Back pressure can be tested from the tailpipe of the exhaust system by determining if enough exhaust flow is passing through it. If you plug the tailpipe with a safety glove on your hand and a thick protective rag and then the engine dies, you have restricted exhaust flow. Since many components comprise the entire exhaust system, this test does not necessarily condemn the converter. An exhaust pressure tester could be used to determine catalyst failure. Drilling a small hole in the pipe in front of the converter and inserting the tester tube to determine if pressure is present would be the next step. If pressure is present in the pipe, then the exhaust flow is not passing through the converter as it should be. -
The oxygen sensor is one of the more common causes of catalyst failure. This happens over a period of time, but the sensor's responsibility to monitor the air-to-fuel ratio expelled from the combustible engine. When it fails, the computer to the vehicle fails to register the information and make the necessary adjustments to the ratio. This can cause either a rich or lean fuel mixture, which will eventually cause internal catalyst failure. Too much fuel will create too much heat inside the converter and cause the precious metals to melt. This will lead to internal breakdown of the converter and most likely cause clogging of the exhaust flow. Too much air will allow undesirable contaminants and pollutants to slowly clog the passage way of the converter as the particles affix themselves to the precious metals.
Catalytic converters are generally constructed of stainless-steel shells. Although durable, it is not out of the question for a weakness in the shell to occur and cause an exhaust leak. This condition will create a loud exhaust noise and will eventually contribute to the internal break down of the converter. -
Other than a visible hole in the shell of the converter, the internal components would far outlive the external shell if the engine is running properly. Spark plug misfires, failed oxygen sensors, leaded gasoline and oil or coolant contaminants are all contributing factors in breaking down the internal catalyst.
When a converter breaks down, replacing it is obvious. Keep in mind that not addressing the catalyst failure will eventually compromise the new converter. Regular tuneups, oxygen sensor interval changing and overall maintenance to the engine to keep it running well will help the longevity of your catalytic converter.
