What you need to know about choosing and installing a catalytic converter

An Information Guide
(This guide has been edited as of April 4th, 2009 to reflect the latest information and technology and how it should apply to the selection process)


We are all too familiar with this scenario: You replace the catalytic converter on a vehicle and the Check Engine Light (CEL) comes on. To the customer, it appears that you, the mechanic, are at fault for poor quality work or installing faulty parts. The customer feels they should have taken it elsewhere, and your reputation is damaged.

We agree that nothing is as difficult to resolve as warranty issues or a converter that cannot consistently perform like it should. That is why we are offering solutions to these problems so that you will have fewer warranty problems, and your customers will be satisfied. To cover this, we feel that you need to be informed about the vehicles and how they operate, so that you can accurately fix the problem.

We have put together a list of things that can be done to do the job right, and to minimize problems with your new catalytic converter.


1 Make sure to install a converter that is certified for the application. Most aftermarket converters are certified by displacement and GVW ratings, but this does not always make them suitable for every application. Common sense must be applied to determine the suitability of a converter for a given application. One cannot install a common round body universal into a full size truck and expect it to work. Likewise, using regular universal converters in a GM car with a 3.1L or 3.4L is a recipe for disaster. Careful planning must be employed to determine the correct converter to use. For the troublesome vehicles, use heavy duty units or suitable aftermarket assemblies that have been tested to work effectively in the intended application.

How does one indentify what vehicles are likely to be troublesome? Check the emissions sticker. If the sticker state that the vehicle meets California emission requirements, or that the vehicle meets Low Emission Vehicle Requirements, then a suitable converter must be used. Low Emission designations include:
Low Emission Vehicles (LEV, NLEV)
Ultra Low Emission Vehicles (ULEV, ULEV-II, ULEV-III, ULEV-IV, ULEV-V)
If your vehicle has this label, then a converter which has been approved for low emission vehicles should be used, otherwise, repeated failures may result. If you are considering purchasing a catalytic converter and the listing or description is unclear as to whether the converter works on Low Emission Vehicles, the part should probably be avoided. Many parts that claim to work on California models may work ok too, but still, look for an LEV designation or some kind of indication that the part is actually intended for your application. If in doubt, contact the seller.

Also, do not be fooled by brand names. While finding brand name products is a good rule of thumb for many things, many of the leading brand names in catlaytic converters are of average or substandard quality. This is especially true of converters marketed under perfomance oriented names. These products tend to put emphasis on outward appearance to entice an uneducated buyer. To truely get the best product, follow the guidelines outlined here.

California statement!!!
As of January 1st 2009, all aftermarket converters sold in the State of California must meet the new California test standards. The new test classes converters by manufactuer, engine family, and test weight. The converter must be certified for specific engine families for specific applications. The product will have a listing of which applications it has been approved for to date. If you are a California resident and are considering purchasing a catalytic converter, check the application listing to see if it meets the new California regulations and is approved for your vehicle. Any products we sell which are California certified will have a clearly worded statement listing which applications it is California legal for. If your vehicle is not listed, then the part cannot be used on your vehicle. These new regulations are in the mean time forcing many customers to the dealership. If you are not a California resident, not of these restrictions apply to you.


2 Replace the O2 sensors. Most O2 sensors are designed to be replaced every 50-80 thousand miles. If the vehicle has more miles than that, the O2 sensors should be replaced. Also, if the vehicle has a Mass Air-Flow sensor, it should be thoroughly cleaned. If the sensors are not replaced, the sensors can be tested for accuracy by following this simple procedure. Please not that this procedure does require a scanner that can read live data output and can access the freeze frame data.

Document all the data on the freeze frame screen. This should include the code of the probelm that trigered the light to come on, as well as temperature readings, load data, etc. All of these parameters can be useful, but most especially the Long Term Fuel Trim (LTFT, LongFT, LngFT, etc.). This value is the average amount of adjustment the computer was making to the calculated fuel requirments. If the computer gets accurate information about engine load, air density, temperature, etc, then it should be able to accurately calculate the correct amount of fuel the engine requires. The O2 sensor(s) should then verify the information, and only moderate adjustments should be required. If more than a 5% adjustment is needed, then one of more sensors is giving the computer false data. O2 sensors are a common culprit, but lots of conditions can affect the calculation.

As a general rule, positive values are often the result of intake leaks, fouled MAF elements, weak or dirty O2 sensors, misfires, poor comustion, or carbon deposits. Negative values are often the result of leaking injectors, or other fuel delivery problems related to the fuel pump and/or pressure regulator.

3 De-carbon the vehicle. This is a particularly important step, and is becoming more important due to the increased sensitivity of OBD-II cars. What happens is the carbon absorbs, then slowly releases oxygen, such that the fuel does not burn completely, and the O2 sensors simultaneously read a lean condition. Carbon deposits also interfere with normal combustion. The ECU enriches the mixture till the O2 reads correctly, but the vehicle is actually running excessively rich. Often, doing a de-carbon treatment (B-12, Sea foam, etc.) through a vacuum line, or doing a carb-vac or similar treatment will resolve these issues. Cleaning or replacing pipe and other exhaust components that have an excessive carbon build up is required.


4 Check the ignition timing. This is often neglected because most newer cars do not have adjustable timing, but checking it can reveal misfires or faulty sensors. This is relatively easy to do on most cars. Excessive ignition advance can lead to excessive NOX emissions, and insufficient advance can lead to excessive Hydrocarbons.


5 Perform an emissions test. This is often neglected because newer cars monitor their own emissions. However, the O2 sensor on a car does just that. It monitors O2 levels. A proper IM testing device monitors actual HC, CO, CO2, and Nox emissions and can help isolate any problems. Any unusual readings, such as high Nox or CO can suggest what areas might be causing the trouble.



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We have additional information regarding troublesome applications that we feel that you should know about so that you can better serve your customer. We will begin with the common ones.


Chevrolet and GMC Trucks
GM trucks equipped with the 5.7L Vortec engine from 1996 through 1999 equipped with the factory tow package (most are) have questionable computer programming. Suggestions to correct this problem are: Good high quality converters. We offer a line of converters for these applications that have an extremely low failure rate. Secondly, replacement of all O2 sensors.

4.3L, 4.8L, 5.0L, and 5.3L equipped models from 1999 - 2003 are equipped from the factory with cats that are too small to meet the needs of towing and hauling heavy loads. The original cats are small 4" diameter round converters, which overheat when the vehicle is operating under load. We recommend replacing these with larger freer flowing converters that are more suitable for trucks. We also carry bolt on assemblies which are designed to meet the flow requirements of these trucks. Many other aftermarket replacements, especially those made from stainless steel, break behind the driver side flange. Our parts are designed to resist thermal and physical stresses, and will not break.


GM cars and minivans
These vehicles often plug up due to a materials defect witht eh factory manifold. Metal particles flake off the inside of the manifold and plug the factory converter. Models equipped with the 3.1L, 3.4L, or 3.8L engines require special high-efficiency cats, especially on the California and LEV(Low Emission Vehicle) models. The solution is to use converters that meet Low Emission Vehicle requirements. Special attention needs to be paid to the 3.8L which often develops injector and fuel pressure regulator problems. If the vehicle has a long term fuel trim of greater than -5%, the fuel pressure regulator should be replaced, along with any faulty injectors.


Volkswagen and Audi
Models equipped with 1.8L Turbo engines are sensitive to being overfilled with oil. If the oil level exceeds the full mark on the dipstick tube, drain off the excess oil, run a thorough fuel injection and combustion chamber cleaner to remove any residual oil and carbon deposits, and replace with a suitable LEV compliant converter.

Volkswagen cars equipped with the 2.0L engine manufactured for 1996 - 2000 model years. Many of these cars were manufactured with faulty MAF sensors, which caused damage to both the O2 sensors and the catalytic converters. Replace these units only with a Low Emission Vehicle compliant converter, and at the same time, replace the O2 sensors and the MAF sensor. Chances are the MAF sensor was already replaced previously as part of a recall, but it is an inexpensive part, and serves as a little insurance. We carry replacement weld-in converters and assemblies that meet LEV standards. The original converters on these cars have a high failure rate on the converter substrate breaking apart. Our converter is guaranteed not to fail for a period of 5 years or 50,000 miles. A de-carbon treatment is also highly recommended. The newer 2.0L engines are not affected by this problem, but still require LEV compiant converter in order to keep the CEL off.


Honda and Acura
Honda Civic CX, LX and DX models made from 1997 to 2000 have a converter with a build in manifold that cracks, causing various converter related codes to be set. The cracks are often not repairable, and repairs are often expensive. Many repairs also fail. The manifold is made from cast iron, making it difficult to weld. The OEM part is expensive and will eventually fail in the same manner. Our current solution is a one-piece steel manifold and converter set. It is of the highest available quality, and resolves the issue. You will also find our cost to be competitive with other lower quality units. Our warranty is 5 year 50,000 miles on the ceramic biscuit, and 5 year 50,000 miles on the body and manifold. Avoid 2 piece manifold converter sets, or units that have cast manifolds.

Honda Civic models from 2001 - 2006 use a new stamped steel manifold, but it still often cracks or splits, resulting in the same kind of failure outlined above. The computer is more sensitive on the newer models, and as a result more powerful LEV compliant converters should be used to prevent repeated failures.

Honda Accord 2.3L & 3.0L, Acura TL 3.2L, Honda Odyssey 3.5L and other Honda and Acura models require very high efficiency Low Emission compliant converters. Many of these models have O2 sensors in the middle portion on the converter body. Most aftermarket converters are not efficient enough to pass the vehicle's self-diagnostics. If non-LEV replacement converter are used, it is highly likely that the CEL will come back resulting in a P0420 code, or other catalyst related code. The O2 sensors should be replaced, and the EGR system should be checked for proper operation. Additionally, the engine should be de-carboned to optimize its performance.


Toyota
Many Toyota vehicles meet Low Emission Vehicle requires. These vehciles require specialized replacement cats that are efficienct enough to keep the CEL off. Standard tune up procedures should be followed, including new O2 sensors every 50,000 - 80,000 miles.

Special notes on the 2003 - 2005 Corolla and Matrix 1.8L (also applies to Pontiac Vibe and Chevrolet Prism). Toyota has issued computer updates which improve the vehicle s fuel trim tables, and adjust the sensitivity of the catlayst monitor and change the test parameters. Make sure your vehicle has this update before attempting to replace the catalytic converters.



Bear River Converters
We are the catalytic converter experts!
Selling superior quality converters, flex pipe, and stainless tips.
Check out our eBay store!

We carry an extensive line of premium quality converters. If you need a converter, we can probably get it for you!
This guide was written by Bear River Converters, the catalytic converter experts. To find a complete line of premium quality converters, flex pipe, and stainless steel tips, visit our eBay store.
To contact us:
Bear River Converters
1877 W. Park Avenue
Riverton, UT 84065

Web: www.bearriverconverters.com
Phone: 888-782-8825 (Toll Free)
Fax: 801-446-4511
E-mail: brc@bearriverconverters.com