How to tell if your RV's catalytic converter is bad

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If you aren’t too car savvy, you might not know what a catalytic converter is or what it does. You might just know it as that car part that commonly gets stolen. But the catalytic converter is an important RV part that serves a special purpose. 

In short, their job is to reduce harmful emissions by chemically converting them into far less toxic substances before they make their way out the exhaust pipe. The reason they are so often stolen is that the part contains precious metals such as platinum, palladium, and rhodium. These are all rare metals, and absolutely essential to modern internal combustion engines, so they are pretty valuable targets for thieves. But like any part of your car or motorhome, you do have to worry about your catalytic converter eventually wearing out and going bad— which is a far more likely fate than theft. 

A worn out catalytic converter can have a big impact on your RV’s performance and cause harm to the atmosphere, so it’s important to make sure your catalytic converter is well maintained and functioning properly. We’ll walk you through some of the signs that your RV’s catalytic converter has gone bad.

1. Your check engine light is on.

This sign should be pretty hard to miss. If the catalysts are no longer doing their job, then your exhaust is going to be spewing out some nasty chemicals. Many cars and motorhomes, especially newer ones, have sensors that will detect that something is wrong and let you know with the check engine light.

A check engine light can mean many things, so if your RV’s information screens don’t show you what the problem is, an OBD may be needed. An OBD is a small electronic device that plugs into a port below the steering wheel and interfaces with the car to produce a code that reveals the issue. An error code of P0420 indicates problems with the catalytic converter. If you don’t have an OBD, you can usually pull up to any auto parts store and have them run a quick diagnostic test for free.


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2. Your RV has failed its emissions test.

To keep your motorhome registered and street legal, you may need an emissions test completed depending on your state or local regulations. A car might fail an emissions test for several reasons, but if your catalytic converter has gone bad, you probably won’t be able to pass. Even if that test isn’t required, regular safety inspections might catch a problem with your catalytic converter. While it's never fun failing an inspection and having to pay for an unexpected repair, it is better to catch a problem there than on the road.

3. You hear rattling noises.

While it’s not the most common issue with the part, catalytic converters can rattle if they sustain damage. The inside of a catalytic converter looks a lot like a honeycomb, and these meshes can collapse or break. This could be due to contact from outside or fuel getting into the converter from the engine, resulting in a small combustion. This can melt and destroy the honeycomb, leading to rattling. If you have the mechanical know-how, you can remove the catalytic converter once it is safe and see if that is the source of the rattling sound. Otherwise, it’s best to get an expert to check it out.


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4. You’re experiencing worse than normal fuel efficiency

If the damage in a catalytic converter is extensive, vapors will have a harder time flowing out the exhaust pipes, or might get stuck all together in the converter. When the flow is restricted, this can cause increased exhaust pressure in the engine, preventing the pistons from filling with the proper mixture of gasoline and air to fire at full efficiency. 

If you notice that you’re having to stop at the gas station more often than usual, you’re calculating a worse MPG everytime you fill up, you should get your catalytic converter checked.

5. You’re having problems starting your motorhome.

If too much exhaust builds up inside your car’s catalytic converter, the pressure can back up into the engine. You will need more power to get the car started, and the initial energy from the ignition might not be enough to overcome the pressure working against it. If it does manage to start, it will likely be slower and feel might take a few tries to get there. 

On a related note, it is important to keep your spark plugs well maintained. If you do have issues starting your car, ruling out your spark plugs can help you get to the problem sooner. On top of that, poor spark plugs can lead to uncombusted gasoline passing into the catalytic converter where it can then ignite and cause damage.


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6. You experience loss of power.

Similarly to the last few signs, the pressure buildup from a damaged catalytic converter can make it harder for the pistons to fire at full strength. Exhaust should normally pass through the exhaust’s tailpipe and have a similar pressure to the atmosphere around it, which is the pressure that pistons are designed to push against when ignited. This loss in power and the loss in fuel efficiency go hand in hand, as you will notice that you might use the same amount of pressure on the gas pedal but get less acceleration. You might also notice that you must increase your pressure on the pedal to compensate, using more gasoline to achieve the same acceleration you normally would. 

Unless you are well-versed in vehicle repairs, replacing your RV’s catalytic converter will likely require a mechanic’s expertise. 

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