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Catalytic Converter FAQs

What is a catalytic converter and how does it work?

Do all cars have catalytic converters?

What does a catalytic converter look like?

What is an "universal" catalytic converter?

How can I select the correct Tier One Components universal catalytic converter for my application?

Is it possible for a catalytic converter to fail?

How can I tell if I need to replace my catalytic converter?

What is an O2 sensor?

Can I prevent a converter from failing?

What does the EPA have to do with catalytic converters?

How do I know I am selecting the right Tier One universal converter for my vehicle application?

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What is a catalytic converter and how does it work?

A Catalytic Converter is an emissions control device installed directly in the exhaust stream of an internal combustion engine for the purpose of reducing the toxicity of the exhaust emissions coming from the engine. During operation, the internal combustion engine produces noxious byproducts which include:

  • Unburned hydrocarbons (unburned gasoline) – producing smog
  • Carbon monoxide – poison for any air breathing animal
  • Nitrogen oxides (created when engine heat forces nitrogen to combine with available oxygen) – leads to smog and acid rain

Inside the converter are small amounts of precious metals (Rhodium, Platinum and Palladium) which are coated onto a ceramic honeycomb substrate that act together as “catalysts” to stimulate a chemical reaction to “convert” the exhaust emissions into less-toxic or inert substances such as oxygen, nitrogen, hydrogen and carbon dioxide.

With the exception of the exhaust gases passing through the converter, there are no moving parts in the catalytic converter. The work being done by the converter is continuous as long as exhaust gases flowing through the converter are able to come in direct contact with the precious metals.

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Do all cars have catalytic converters?

Starting with the 1975 model year, the U.S. Environmental Protection Agency (EPA) initiated regulations that tightened standards for auto exhaust systems. In order to comply with these regulations, catalytic converters were developed and approved as a means of achieving compliance with the EPA regulations.

If your car was built after 1974, it is equipped with a catalytic converter.

Today, catalytic converters are used on automobile exhaust systems as well as trucks, buses, generator sets, forklifts, trains, airplanes, and other machines equipped with internal combustion engines.

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What does a catalytic converter look like?

The catalytic converter on your vehicle can be found in the exhaust system underneath your car. You can trace your exhaust system to find your catalytic converter by starting at the "tail pipe" at the rear of the vehicle. Moving toward the front of the vehicle you will first find one or two mufflers, depending upon whether your vehicle has a single or dual exhaust system. As you continue to trace the exhaust system toward the front of the vehicle, you will find other metal cans that may look like mufflers. The converter will be the one or possibly two that are closest to the engine (some vehicles are equipped with a small "pre-converter that is installed very close to the exhaust manifold on the engine.

Vehicle manufacturers have developed many different catalytic converter shapes. These shapes include: round, oval, and flat "cans" with a variety of inlet and outlet tube diameters.

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What is an "universal" catalytic converter?

The "universal" catalytic converter is a low cost alternative to replace a defective converter without replacing all of the costly pipes and components that are still in good working order on the vehicle.

Over the years, automotive vehicle manufacturers have developed hundreds of catalytic converter designs for their vehicle and engine applications. Many of these converters were welded into exhaust assemblies with complex bent tubes to create a unique product design for a specific vehicle application.

This process is very efficient for the original equipment manufacturing systems, however it creates a part number and cataloging nightmare for replacement parts required to service catalytic converters over the life of the vehicle.

A universal catalytic converter is designed as an efficiently packaged catalyst capable of being installed into many different vehicle applications by simply removing the existing converter and installing the universal converter in its place. This is substantially less expensive than removing and replacing the complete OEM converter assembly.

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How can I select the correct Tier One Components universal catalytic converter for my application?

The Tier One Components universal catalytic converter has been tested and approved by the EPA for 49 state vehicle replacement applications based upon the displacement of the engine in the vehicle. Selecting the correct converter is easy and should be based upon the vehicle you are working on.

  1. You can enter the vehicle type, model year, and engine size into the "Search By Vehicle" block in our website. We will then provide you with the proper universal converter for your requirements.
  2. If you have already located the converter you are replacing on your vehicle, you can also select the converter by taking your own measurements:
    • Engine size – We have converters for engine sizes up to 5.9 liters. If your engine is larger than 5.9L with a single exhaust system, we do not have a universal converter to fit your application.
    • Exhaust Tube Diameter – We have three (3) standard size exhaust tube diameters our converters are designed to fit – 2.00", 2.25" or 2.5".
    • Overall length of the replacement converter – 13.00" or 16.00"
  3. Exhaust Tube Diameter (OD)

    2.00 inches

    2.25 inches

    2.50 inches

    Overall Length

    13.00 inches

    16.00 inches


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    Is it possible for a catalytic converter to fail?

    Typically, when a catalytic converter fails it is a result of some other component or system in the engine that fails causing the converter to become clogged or poisoned.

    In order to operate properly, the converter must receive the proper mix of exhaust gases within the proper temperature range. There are some additives or engine system malfunctions that will cause the temperature or mixture of exhaust gas to change. If these changes are outside the proper engine operating specifications, extended exposure can reduce the effectiveness and life of the catalytic converter. Leaded gasoline and the over-use of certain fuel additives can shorten the life of a catalytic converter.

    In addition, the converter can become the victim of fouled spark plugs, causing unburned fuel to overheat the converter.

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    How can I tell if I need to replace my catalytic converter?

    The most obvious indicator can be the “Check Engine” light. There are a number of circumstances that can cause the “Check Engine” light to come on; one of those could be indicating a problem with your catalytic converter. However, just because the indicator light is on, this does not necessarily mean you need to replace your converter. A professional mechanic with proper diagnostic equipment should be able to conduct the proper tests to determine if the converter needs to be replaced.

    There is no visual method for you or your mechanic to “see” an actual defective converter. Rather, you may have detected a gradual change in the performance of your engine. You can temporarily remove the converter to check for a noticeable change in engine performance. Some mechanics will temporarily remove the Oxygen Sensor (O2 Sensor) from the exhaust pipe ahead of the converter to again check for a change in engine performance.

    Other indications of a defective or failing converter might be:

    • The vehicle is not responding to increased throttle pressure.
    • Vehicle fuel mileage has decreased significantly.
    • If the converter is partially blocked, it can act like an engine governor by limiting the engine RPM’s to a fast idle speed and not allowing the engine to achieve normal RPM’s during driving.
    • A totally blocked converter will increase engine back pressure causing the engine to stall after a few minutes.

    Catalytic converters are an expensive component in your vehicle exhaust system. Therefore, if you are considering replacing the catalytic converter on your own and there is any doubt as to whether you actually need or require a new converter, we would recommend that you allow your local professional engine mechanic to run some simple tests to confirm that you actually do need to replace your converter. Seeking the opinion of a professional might actually save you money if you don’t need to replace your converter at this time.

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    What is an O2 sensor?

    Every new car being manufactured is equipped with at least one O2 Sensor (Oxygen Sensor). This sensor has been installed in all vehicles starting in 1980. The O2 sensor is an integral component of the vehicle emissions control system. Typically, it is installed in the exhaust pipe ahead of the catalytic converter and continually analyzes the presence of oxygen in the engine exhaust stream providing continuous data to the onboard engine management computer to help the engine run as efficiently as possible and to minimize vehicle emissions.

    When an engine has excess fuel in the exhaust after combustion it is described as “running rich.” On the other hand, if the exhaust stream has excess oxygen after combustion it is described as “running lean.” Automotive engineers have determined an ideal ratio of air to fuel (stoichiometric mixture) to insure the engine runs optimally. The ideal ratio is 14.7:1, i.e. 14.7 parts of air to each part of fuel. If the ratio is “rich” there is excess fuel which means unburned fuel in the exhaust stream and therefore excessive emission pollution. On the other hand, if the ratio is “lean” the result is more nitrogen-oxide pollutants which can cause poor performance and even result in engine damage.

    Located in the exhaust pipe, the O2 sensor is capable of detecting whether the engine is running “rich” or “lean.” It does this as a result of a chemical reaction in the sensor that generates voltage proportionate to the stoichiometric mixture. The engine’s computer monitors the voltage from the O2 sensor and automatically adjusts the amount of fuel entering the engine based upon whether the mixture is rich or lean. Because there are a number of factors that can influence the oxygen content in air, the O2 sensor must be working properly at all times so the engine operates with the proper air/fuel ratio. Some of the factors that can influence oxygen content are; altitude, air temperature, engine temperature, barometric pressure and the load on the engine.

    If the O2 sensor fails, the engines computer can no longer sense the actual air/fuel mixture so it ends up “guessing” which causes your car to perform poorly and to consume more fuel than it needs to.

    As a result, a defective O2 sensor can contribute to pre-mature catalytic converter failure.

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    Can I prevent a converter from failing?

    The easiest preventative action you can take is to maintain the ignition system of your vehicle in top shape. This will provide the most efficient combustion performance and prevent unburned fuel from entering the catalytic converter.

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    What does the EPA have to do with catalytic converters?

    The Environmental Protection Agency (EPA) establishes national rules and laws that apply to the use and replacement of catalytic converters. In addition, some states have enacted more stringent emission standards which also can affect the performance of the emission control systems on your vehicle. Businesses involved in servicing vehicles must comply with both federal and local guidelines, or face fines and/or the loss of business permits and licenses.

    In all states, it is illegal to have the catalytic converter removed without installing a replacement converter in the vehicle. No vehicle is allowed on the road without a catalytic converter. Most states require an emissions inspection and a vehicle without a catalytic converter cannot pass this inspection.

    Most federal guidelines state that replacement converters may be installed only in the following situations:

    1. A state or local inspection program has determined that the existing converter needs replacement.
    2. Vehicles manufactured prior to 1996 must have more than 50,000 miles and a legitimate need for replacement must be established and documented.
    3. In cases of OBD II equipped vehicles (1996 and later), the O.E. manufacturer's 8-year/80,000-mile warranty must have expired and a legitimate need for replacement must be established and documented.

    (Note that Federal law prohibits removal or replacement of a properly functioning O.E. converter). Other laws and guidelines state that:

    1. The replacement converter be installed in the same location as the original.
    2. The replacement is the same type as the original, i.e., two-way, three-way, three-way plus air/three-way plus oxidation.
    3. The new converter is the proper model for the vehicle application as determined and specified by the manufacturer or certified by the EPA for the vehicle application. (NOTE: The Tier One Components Universal Catalytic Converters have been certified by the EPA for use in the 49 states excluding CA.).
    4. The replacement converter is properly connected to any existing air injection components on the vehicle.
    5. The new converter is installed with any other required converter for a particular application
    6. The new converter must be accompanied by a warranty information card to be completed by the installer.

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    How do I know I am selecting the right Tier One universal converter for my vehicle application?

    If you know the displacement of your engine, the diameter of the exhaust pipe and the length of the gap that will be opened when your current converter is removed, you can easily select the right Universal Converter from our product line.

    If you are seeking additional confirmation, you can enter your vehicle make, model and powertrain information into our online catalog and we will help you select the proper replacement.

    If you and your vehicle are located in California, you will not be able to select a Tier One Universal Converter at this time. Tier One will be developing Universal Converters in the future that will be approved for use by the California Air Resources Board (CARB) however, those products are not available today for you to purchase for your California vehicle application.

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