Catalytic Converter Replacement

To car enthusiasts, catalytic converters are often viewed as a government conspiracy to limit horsepower. This is because catalytic converters are the least-understood emissions-system component. In reality, the "cat" performs a vital function: converting many toxic byproducts of internal combustion into harmless carbon dioxide and water vapor.

Legalities
In general, the EPA mandates that catalytic converters can't be replaced in vehicles having less than 50,000 miles unless the converter is damaged due to accident. This legislation is intended to minimize emissions-system tampering. Most vehicle manufacturers warranty the emissions components for 50,000 (or more) miles anyway, so cat failure in newer vehicles is often covered. The gist here is that catalytic converter replacement is illegal in some instances, regardless of whether the job is performed at home or at a service center.

Catalytic converters are the least-understood emissions-system component.
Most motorists are blissfully unaware of their cat's condition until their vehicle fails an emissions test. On the other hand, hands-on people who are willing to get down and dirty might recognize a hole (or holes) in their converter. Also, a sure sign that an older car's cat is shot is when the pellets break free and roll around in the converter's housing, sounding like marbles being shaken in a coffee can.

DIY
A quick creeper-cruise under the raised-and-secured vehicle can determine if cat replacement is an at-home possibility. If the vehicle still has all its original exhaust components, the job might be a proverbial (and usually fallacious) bolt-on. However, if the muffler and/or intermediate pipes have been replaced at a muffler shop, the resulting welds might add an extra degree of difficulty. If this is the case, people who don't have welding-and-cutting skills and equipment should probably have a shop do the job.


The obvious advantage to replacing your own cat is cost savings. The car shown in the accompanying Steps still had its original converter, and the pellets finally vibrated free at about the 190,000-mile mark. A muffler shop quoted $195 for parts and labor—about one-fourth the vehicle's Blue Book value. In contrast, replacement cats from the parts store ranged from roughly $60-$75 for this particular 1988 GM N-body car. (Strangely, the direct-fit converter was cheaper than a universal cut-to-fit model.)