4 Primary Reasons for Catalytic Convertor Failure – Emission Repair and Service in Everett, Mukilteo, Snohomish and Lynwood Washington

One of the worst things to hear from your emission testing station is that your car has failed the mandated emission standard. Chances are, however, that you have noticed a decrease in fuel efficiency over time. The fact of the matter is that if the catalytic convertor has failed on your vehicle that failure is actually a symptom of a more serious problem. It is essential that the underlying problem be diagnosed and repaired prior to replacement of the catalytic convertor. Without proper repair of the engine problem, your new catalytic convertor will ultimately suffer the same fate – failure!


The substrate can be destroyed by:

  • Antifreeze
  • Leaded Gasoline
  • Zinc in some oil additives
  • Some silicon sealants

If antifreeze has found its way into the exhaust system, it is crucial that the problem be located and repaired. Using leaded gasoline in any vehicle with a catalytic convertor will cause severe damage and the fuel lines would need flushing or replacement. Be extremely mindful of reading the labels on any oil additives and silicon sealants to insure ingredients will not harm the catalytic convertor.


If a catalytic convertor’s substrate is either coated or plugged with oil, an engine leak is indicated. You will likely notice a drastic increase in oil consumption which could indicate excessive engine wear. Again, the engine must be repaired/replaced as indicated before replacing the catalytic convertor.


An overheated substrate will show excessive amounts of:

  • Hydrocarbons
  • Carbon Monoxide
  • Oxygen

Generally, when the substrate is melted or overheated, the cause can be narrowed to one of the following problems:

  • Poor fuel control
  • Poor quality of fuel
  • Worn or failed O2 (oxygen) sensor
  • Restricted air cleaner
  • Excessive engine load
  • Poor spark or weak ignition
  • No engine compression

Regardless the severity of the underlying issue that caused substrate overheating or melting, it must be repaired!


Damage can occur to the structure of a catalytic convertor in any number of ways. Perhaps the most common damage is due to road conditions such as deep pot holes that dent the outside of the unit. In addition to collision damage, there are other, less obscure situations that will damage your catalytic convertor:

  • Corrosion from road salt
  • Metal fatigue
  • Stripped O2 sensor plug
  • Failure at the flanges of the inlet/outlet pipes

A potential hazard, especially if your convertor is operating at very high temperatures occurs in winter. If your vehicle passes through icy-cold water the extreme temperature change will quench the convertor and cause metal fatigue.

It is essential that any failed catalytic convertor be replaced immediately. It is wise to have the Emission Repair in Everett, Mukilteo, Snohomish and Lynwood diagnose and repair the underlying issue. Replacing a catalytic convertor can be quite costly, and if you do not take care of the reason for the failure – it will continue to fail.