Raw Fuel in Catalytic Converter – What’s Wrong and How to Fix?

The health of your catalytic converter is very important. This is quite an expensive part – the OEM converter may cost several thousand dollars if you add up its price and the labor costs. Even if you buy the aftermarket converter to change the broken one, you will have to pay quite a lot. So, it’s natural that you may want to prolong the life of the converter in your car as much as possible.

In short, raw fuel in your converter kills it very fast because it leads to severe overheating inside the catalytic converter, so it’s always a bad idea to allow the fuel to get there. Fuel may get to the catalytic converter if there are problems with injection and ignition. Also, misfiring cylinders may lead to such issues.

Here’s what I will cover in this article:

• How can raw fuel get into the catalytic converter?
• Best ways to prevent this from happening.
• What are the consequences of raw fuel in your cat converter?
• How else can you prolong the life of the converter?

Raw fuel in your cat converter – symptoms and consequences

Before I tell you how to cope with this problem, you need to understand how the combustion process work and how potentially raw fuel can get into the exhaust system and then into the catalytic converter.

The healthy engine will burn the majority of fuel and only some vapors may get into the exhaust system. They then burn in the pre-cat (if there is a pre-cat) and also in the catalytic converter. This is OK and the unit is ready for such conditions.

But when the engine has some problems and the combustion process is not completed as it should, not only vapors but also some raw fuel may eventually get into the converter.

Here’s how it happens:

• the air-fuel mixture gets into the combustion chamber but there is no spark and it isn’t ignited;
• the fuel then partially goes down the engine block to the oil pan and some part of it gets to the exhaust system through the exhaust valves;
• in the exhaust system, the fuel usually gets into the catalytic converter that is mounted right after the exhaust manifold;
• the temperature in the converter is very high, so the fuel is burnt there or rather explodes in the converter;
• these explosions and the burning process are very harmful to the unit and may cause its premature death;
• also, the car may backfire if the problem continues to torture your vehicle.

So, the majority of the raw fuel that gets into the exhaust system will explode or burn inside the catalytic converter. Some of this fuel may also burn further and destroy the muffler, and the pipes and even come out of the exhaust pipe in the form of fire. This may look cool when you drive but it’s not cool for the entire exhaust system.

So, if you notice backfiring, feel that the catalytic converter is too hot (sometimes even red-hot), the engine loses power and misfires, there is a check engine light prompting that the vehicle has problems with exhaust, you should check this as soon as possible. Chances are the unburnt fuel is now killing the catalytic converter and your vehicle needs urgent help.

How can raw fuel damage your catalytic converter?

Now, that you know how this problem starts, I should turn to the most important part of the article and tell you what exactly happens with the catalytic converter when fuel explodes or burns in it.

First of all, you should know that catalytic converters are made to withstand quite high temperatures. They are always hot when the engine works. But they shouldn’t be red-hot. When a catalytic converter overheats, bad things happen to it.

Here are the results of this:

• tender ceramic honeycomb suffers because of small explosions and may get some cracks and other micro damages;
• burning fuel will overheat the converter and can even melt it inside, this will largely affect the way it works;
• also, this will form a lot of soot and black buildup – the products of burning will stick to the insides of the converter and will clog some parts of it;
• step by step, these factors will affect the converter’s ability to do its job;
• in bad cases, the complete working part of the catalytic converter may be destroyed;
• when this happens, the converter doesn’t work with exhaust gases and this triggers a code in the ECU telling you that there is a problem with the exhaust system.

I’ve seen completely empty catalytic converters. When the ceramic honeycomb that is inside the converter starts destroying, it falls apart pretty quickly. If the converter is located under the car, the parts are blown away through the exhaust pipe. But if it’s located in the exhaust manifold, like in some KIA and Hyundai vehicles, for example, these small ceramic parts may be sucked into the engine and hurt it badly.

But let’s focus on the catalytic converter and the effects that it will feel when the fuel burns in it. Unfortunately, this situation will launch the slow death of the converter and will inevitably kill it after some time if not addressed immediately.

Preventing raw fuel from getting into the catalytic converter

First of all, you should understand the symptoms that may signal the problem with the catalytic converter and tell you that some fuel is burnt inside this part, not in the combustion chamber.

Here are some of the symptoms:

• the catalytic converter is abnormally hot after you drive the car for some time;
• there is the check engine light and the code tells you that there are problems with oxygen sensors;
• also, the check engine light may tell you about the misfiring of one or two cylinders;
• the gas mileage dropped and now you need to burn more fuel to go a certain distance;
• you feel that the engine lost its effectiveness;
• you can’t pass the emission test – there are fuel fumes in the exhaust;
• the exhaust has a sharp smell of something burnt, there may be black smoke from the tailpipe.

Unfortunately, all of these symptoms may also mean some other problems. So, whenever you encounter some of them, check if the problem is because of the catalytic converter issues.

When it comes to your actions, you can still drive such a car. The effect on your catalytic converter will not be immediate. But it only means you can drive it several miles and then go to professionals to have it inspected and repaired.

Here’s what you will need to do to prevent problems from happening:

1. Check the ignition system. It’s important to understand that all the fuel is ignited correctly and in the needed time. If some deviations are spotted, repair the ignition system as soon as possible. This can be just as simple as replacing a spark plug or a coil.
2. Check the injectors. Injectors must atomize the fuel that they inject into the intake manifold or into the combustion chamber (direct injection). If the fuel is not atomized, it will not burn completely and some part of it may go to the catalytic converter.
3. Check compression in each cylinder. Low compression may be the reason why some fuel is not burnt as it should. If compression is low, you will have to find the reason and repair the engine. Sometimes, it’s just the head gasket, but it also can be a more serious problem.
4. Read all error codes. Sometimes, the OBD2 scanner will help you understand the reason for the problem for just some minutes. Read all the codes, clear them, test-drive the car, and then read the codes again. They may clearly show you the initial problem.
5. After the repair, make sure the engine works smoothly. Pay attention to power, gas mileage, idling RPM, and other factors. Also, make sure the check engine light is not going on the dash anymore.

After you drive several miles and you have the possibility to get under the car, make sure the catalytic converter is just hot, not red-hot. But never touch it with your hands – just look at it and you will see if it’s overheating.

Following these simple recommendations, you may prevent raw fuel from getting into the catalytic converter. This will save its life and prolong the time of its service.

How else can you prolong the life of the cat converter?

Actually, the temperature of your catalytic converter is the key factor for its longevity. If it overheats, the unit will not last long enough. Also, prevent any kinds of physical damage – for example, you may hit the converter over some rock or another road obstacle.

If the converter is often in contact with water, it may rust heavily. The rust may destroy its shell and lead to holes in the metal cover of the converter. Once there is a hole, the converter will start deteriorating quickly. So, just have a look at the converter sometimes and make sure it’s not destroyed.

You can’t pass an emission test with a broken or damaged converter, so you will have to replace it. Unfortunately, the price for the new catalytic converter is not going to cause any positive emotions, so try prolonging the life of the original converter as much as you can.