The catalytic converter in a vehicle is part of the exhaust system located between the exhaust manifold of the engine and the muffler. Its sole purpose is to control vehicle exhaust emissions. It converts toxic byproducts of the internal combustion process that are present in the exhaust gas and catalyzes them into less environmentally toxic substances. That might make you think cleaning a catalytic converter is a smart thing.
The catalytic processes involved are reduction and oxidation. The reduction process converts any oxides of nitrogen into carbon dioxide, water and nitrogen. The oxidation part of the conversion process takes carbon monoxide and unburned hydrocarbons and converts them into carbon dioxide and water. As most vehicles now have oxygen sensors both before and after the catalytic converter in the exhaust system, any time the catalytic converter becomes clogged, it will directly affect the operation of the vehicle's engine.
Can you clean a catalytic converter?
The short answer: You can't. Once the converter becomes clogged, mechanics and repair experts collectively will tell you that it has to be replaced. Despite the large number of advertisements and misinformation put out on the Internet, no cleaning product or process will restore a catalytic converter to its original capabilities. Any cleaning product may, at best, have an effect that is extremely short-lived. In the long run, from a big-picture perspective, cleaning a catalytic converter is highly inadvisable.
Potential damage to your vehicle
Original equipment manufacturers install catalytic converters in newly assembled vehicles assuming that they will last approximately 100,000 miles. If a catalytic converter becomes clogged well before that mileage mark, it means that there is another problem causing the catalytic converter to become prematurely fouled. Any attempt to clean it, regardless of how futile it may be, will do little more than avoid investigating the cause of the problem.
Engine oil contains phosphorous. If the engine oil is getting into the combustion chamber, it can eventually run down into the exhaust manifold and then into the catalytic converter. If you have a cylinder head gasket that is leaking, the coolant can also get into the combustion chamber and eventually the catalytic converter. Both phosphorous and silicon are common villains with respect to premature clogging of catalytic converters. By expending the time, money and energy to attempt to clean a catalytic converter, you are wasting resources that could be used to address a problem that could be fixed-and avoid catastrophic engine failure.
Legality of cleaning catalytic converters
In states that require automotive exhaust gas testing, tampering with a catalytic converter is illegal. The vast majority of reputable mechanics and repair shops won't consider working on a vehicle in which the catalytic converter shows evidence of tampering.
Efficiency issues with a faulty catalytic converter
The engine control unit (ECU) uses the information that it gets from the mass air flow sensor and the oxygen sensors before and after the catalytic converter to balance and deliver the appropriate fuel mass to the engine. Attempts to clean the catalytic converter, either through chemical methods or by boring through the internal honeycomb with a drill, will result in erroneous information going to the engine control unit. This will cause the engine to receive an incorrect air/fuel mixture, which will not only result in reduced gas mileage but cause poorer engine performance and perpetuate any underlying problems that may exist.