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Subaru Legacy Catalytic Converter

The Common Causes of a Faulty Subaru Legacy Catalytic Converter

Your Subaru catalytic converter is responsible for transforming toxic byproducts of combustion in the exhaust into less-toxic substances by way of catalyzed chemical reactions. Because of its importance, driving a car without this component has been made illegal in the United States. In order for you to stay out of trouble, be on constant alert for signs of a failing catalytic converter. Here are some problems that you may encounter:

Catalytic congestion

The most common cause of catalytic converter failure is congestion, as this usually happens in older cars. Over time, this component can become so clogged that the exhaust gases can't get through it. If air can't get out of the rear of your car, new air can't flow into the front end either. Because no air is coming in to form the fuel/air mixture in the exhaust, the engine then dies.

Surface contamination

A clogged catalytic converter is not the only cause for the component's failure; a contamination in the catalyst can cause it to go bad as well. If this happens, high carbon monoxide (CO) and hydrocarbon (HC) gases will be present in the exhaust system.

To confirm this diagnosis, use a high-temperature digital pyrometer-or an oven thermometer if you don't have access to the first tool. With this, check the catalytic converter's temperature before and after you start the engine. If the component runs 100 degrees Fahrenheit hotter at its outlet than at its inlet, then it is still good. However, if there is little- to no-temperature change, either your car has a problem with low efficiency or it has a problem with the catalytic converter's air supply.

Inspect the air injection pump, belt, and check valve as well. If you think that the check valve is allowing the exhaust to flow backwards, then remove it and blow through both ends. It should let air pass only in one direction but not in the other.

Examine the air injection manifold, too, because it tends to rust and leak air. Lastly, check the diverter valve to make sure it is working correctly. It should be routing air to the converter when the engine is at normal temperature.

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  • How to Maintain the Efficiency of Your Subaru Legacy Catalytic Converter 27 February 2013

    Your Subaru Legacy catalytic converter transforms harmful exhaust gases produced by the engine into less-harmful emissions before they leave the vehicle's exhaust system. These toxic gases-carbon monoxide, hydrocarbon, and nitrogen oxide-are converted by a catalyst into carbon dioxide and water. Because this component is a crucial part of your car and is very expensive, the catalytic converter is built to last for as long as the vehicle's life. It does not require too much maintenance on the part itself, either. However, there are ways for you to maximize a catalytic converter's lifespan and keep it from failing.


    Tips to preventing catalytic converter failure

    To avoid problems with your car's catalytic converter in the future, the first thing to do is to keep your engine and other systems in top shape with regular maintenance and tune-ups. You can see the maintenance schedule of your car's systems in the owner's manual.


    Because a catalytic converter is known to become less efficient every 150,000 miles, schedule maintenance for your car's exhaust system every time your car reaches this mileage. It also doesn't hurt to do it more frequently, e.g. every 75,000 miles.


    Check the pores in the catalytic converter for any dirt and grime that may have started to build up. You can use an auto cleaner to remove any loose residue. If there are buildups that have stuck to the component, use the tip of a small screwdriver to carefully remove these from the pores.


    Other tips and warnings

    Do not tinker with the catalytic converter when it is still under warranty or else the manufacturer will void it should you suddenly damage the component. It is better to start cleaning or repairing it once its warranty expires.


    If the catalytic converter malfunctions within the warranty period, just contact the manufacturer and send the component back for repairs or replacement.


    Before having your car's catalytic converter replaced, make sure to identify the root cause of the component's failure. A faulty car part is always due to a problem with another component or with the system, and if it's not resolved, this same issue could cause the new component to fail.