There are a couple of ways you could unclog a catalytic converter, but it’s important to note that these methods only work on a converter that is only mildly clogged and that is not damaged in other ways. Though it may be impossible to ascertain the condition of the catalytic converter while it’s still on the vehicle, there are two ways to attempt to unclog the converter – on or off the car.
Though you won’t know the true condition of your catalytic converter without removing it, the first step would likely be to use a catalytic converter cleaner that is added to your fuel tank. These chemicals work to not only unclog the converter, but may also help to clean the fuel system and oxygen sensors at the same time. How you use these products depends on the type of product and the manufacturer, but they are often added to a specific amount of fuel and the vehicle is driven for a period of time to allow the product to travel through the engine and exhaust. If you notice performance improvements or less black smoke from the exhaust once you’ve done this, you may have unclogged your catalytic converter. If nothing changes, this may mean that the converter is too clogged for the product to work properly, or that it is damaged in another way that will require replacement.
Since their introduction, catalytic converters have had a bad reputation for a couple of reasons. The first of these is that they are pretty expensive to replace if they clog, or if they’re stolen for the valuable metals they contain. Another issue is the long-standing myth that catalytic converters actually reduce gas mileage by obstructing the exhaust system, however this isn’t actually true of a new or well-maintained converter. The truth of the matter is that a functioning catalytic converter doesn’t have any adverse effects on fuel mileage and significantly reduces pollution. But catalytic converters can clog or fail over time, resulting in a loss of performance and efficiency, and knowing more about your catalytic converter can help you determine when it may need attention or repair.
What Does a Catalytic Converter Do?
Catalytic converters are designed to reduce pollution by using a ceramic honeycomb coated in reduction and oxidation catalysts. These catalysts react chemically with gases in the exhaust to convert nitrogen oxide and carbon monoxide to nitrogen, oxygen, and carbon dioxide before they leave the exhaust system. These compounds are less harmful to the environment and can help minimize the pollutants released into the atmosphere when the vehicle is running.
Reduced Fuel Mileage
When your catalytic converter is clogged, it can cause a buildup of exhaust back pressure which can choke the exhaust system and cause your engine to burn more fuel to compensate. Though you may not notice gradual changes in fuel efficiency as your catalytic converter continues to worsen, a sudden obstruction can cause a drastic drop in fuel mileage, and the converter may need to be inspected, cleaned, or replaced.
An Active Check Engine Light
In older vehicles, oxygen sensors were installed ahead of the catalytic converter to determine the oxygen concentration of burnt fuel and make adjustments accordingly. In more modern vehicles, there will also be an oxygen sensor behind the catalytic converter to perform readings once the exhaust gases have been neutralized. If the converter is clogged or not working as it should, the oxygen sensor may send a signal to the engine control unit (ECU) that causes the Check Engine light to activate. The catalytic converter should be a consideration when you get any type of exhaust-related trouble codes. If you don’t have a code reader or scan tool at home, visit your local O’Reilly Auto Parts, where we can read Check Engine light codes for free.
Rattling Noises from the Engine or Exhaust
It’s possible for the honeycomb inside the catalytic converter to break loose inside the metal body, or to suffer damage due to physical contact with debris under the vehicle or especially rich fuel mixtures. If the honeycomb is damaged, it can cause rattling noises, or pieces of the converter could also eventually find their way out of the exhaust system. Not only can loose pieces of your catalytic converter clog the exhaust system, but when this happens, the converter is also unable to control pollutants. If rattling noises seem to be coming from the catalytic converter, it may need to be replaced.
Engine Misfires
Back pressure in the exhaust system of your vehicle can lead to problems with the fuel mixture. This means that the engine management system may compensate for this pressure with a lean or rich fuel concentration in the cylinders. Too little fuel may cause misfires from the engine, and too much fuel can foul spark plugs and prevent them from firing, also resulting in misfires.
On the other hand, engine misfires can also cause catalytic converter failure. Unburned fuel can exit the cylinder if ignition does not take place, and with time, raw fuel can damage the catalytic converter internally. It is best to fully diagnose and repair any misfire promptly to prevent damage to other systems. Since misfires also generate Check Engine light codes, these can be read to help begin your diagnosis.
Engine Jerking, Stalling, or a Lack of Power
Exhaust clogs, especially clogged catalytic converters, prevent the engine from 'breathing' as it should. This means that it has to work harder to perform its most basic functions. If your catalytic converter is clogged, you may experience a lack of power or reduced ability to accelerate quickly as the engine tries to compensate for the difference in internal pressures. Your acceleration may also be inconsistent, which can cause the vehicle to jerk. Finally, if the catalytic converter is extremely clogged, the exhaust pressure buildup could cause the engine to stall while driving.
The Smell of Rotten Eggs or Sulphur
If your catalytic converter is clogged or not working as it should, you may also notice the smell of rotten eggs due to sulphur buildup escaping the exhaust system. If you notice this smell, it means that the catalytic converter is no longer doing its job, and excess pollutants are escaping from the exhaust system. Though this may not necessarily cause noticeable performance issues, it should still be addressed as soon as possible.
A Failed Emissions Test
If you live in an area where emissions testing is legally required to license and operate your vehicle, a clogged catalytic converter might be enough to cause your vehicle to fail this test. If this happens, you will have to repair the problem before you can register and license the vehicle, and this may require you to either clean the catalytic converter or have it replaced at a repair shop, depending on its condition.
Some catalytic converters may be too clogged for cleaning chemicals to work, and you may need to remove the converter from the vehicle. Many catalytic converters simply bolt on, but it may be necessary to soak the bolts in penetrating oil in order to remove them without damage. It may also be necessary to disconnect the oxygen sensors, depending on their proximity to the converter. Once the converter has been removed from the vehicle, it should be inspected for signs of physical damage. From there it can be cleaned with a pressure washer and degreaser, then allowed to dry and reinstalled using the appropriate catalytic converter gaskets.
Though some catalytic converters are designed to simply be unbolted and removed for replacement, others may be welded on and can require cutting and welding equipment for removal and installation. In many cases, exhaust service and catalytic converter should be handled by a qualified service facility. If you’re not comfortable diagnosing or replacing the catalytic converter on your vehicle yourself, your local O’Reilly Auto Parts can recommend a local repair shop, or you can find a repair shop near you with our helpful online tool. If you’ve noticed a reduction in performance or other problems with your vehicle, it’s a good idea to have it diagnosed as soon as possible to reduce the risk of further damage and ensure your emissions system is working at its best.