Can You Drive A Car With A Bad Catalytic Converter?

Can you drive a car with a bad catalytic converter? This is a question that many vehicle owners often find themselves pondering. Catalytic converters play a crucial role in reducing harmful emissions and ensuring your car meets environmental standards.

However, when this vital component starts to malfunction, it can lead to various issues.

In this article, we’ll explore the consequences of driving with a bad catalytic converter and whether it’s a safe and viable option.

Before delving into the question at hand, let’s briefly understand what a catalytic converter does.

Can You Drive A Car With A Bad Catalytic Converter

The catalytic converter is an integral part of your vehicle’s exhaust system, primarily tasked with reducing harmful emissions, such as carbon monoxide, nitrogen oxides, and hydrocarbons, that are produced during the combustion process.

It achieves this by facilitating chemical reactions that convert these pollutants into less harmful substances, like carbon dioxide and water vapor.

Driving With A Bad Catalytic Converter

If your car is showing symptoms of a bad catalytic converter, such as engine misfiring, loss of power when accelerating, or fuel vapor, you may be curious as to whether driving with a bad catalytic converter is okay or not, and how many miles you can drive with it.

Can You Drive A Car With A Bad Catalytic Converter

Driving with a bad catalytic converter is not too dangerous. If some small parts of your catalytic converter are plugged in, you can still drive your car as usual.

You will see that there is a drop in the performance of the catalytic converter. In the case that the catalytic converter is totally plugged, it will prevent you from running your vehicle.

In some situations, it may come to be completely fused directly or over time, and it will need to be replaced immediately.

Is It Safe to Drive With a Bad Catalytic Converter?

The short answer is NO. Driving a car with a faulty catalytic converter (CAT) is fairly unsafe.

What to Expect When Driving With a Bad Catalytic Converter

First, please understand we do not recommend driving with a bad catalytic converter. Although you may hear that driving with a faulty CAT isn’t too dangerous, let’s walk you through what could happen:

When Your Catalytic Converter is Partly Clogged

A partly clogged catalytic converter won’t stop your car from running, it’ll only have a minimal impact on your vehicle’s performance.

However, suppose you continue to drive with your partially clogged catalytic converter.

In that case, you’ll experience engine misfire or loss of acceleration power.

When the Catalytic Converter is Completely Clogged

You shouldn’t drive your car if a catalytic converter is completely clogged. If you do, you can expect the restricted exhaust flow to hinder your engine performance, which leads to your engine idling for a few minutes and then dying.

Worst case scenario, catalytic converter failure could affect your engine so badly that it won’t start.

Performance problems caused by your clogged converter can become especially dangerous in heavy highway traffic.

On top of that, if smog checks are essential where you live, you’ll only be able to drive your car legally if you replace the broken catalytic converter.

When the Catalytic Converter is Burned Through

In some cases, your catalytic converter will eventually burn through completely. If this happens, you’ll have to replace it immediately.

This problem usually happens if your engine burns too much oil, which means you have another problem to deal with.

If you need more than the above section to deter you from driving with a broken catalytic converter, and you’re wondering how long you can keep going before your car ultimately gives in — let’s take a look.

How Long Can You Drive With a Bad Catalytic Converter?

You can drive your car indefinitely with a partially plugged converter. But we do not advise this as it’ll affect your car’s performance and possibly cause problems to build (on top of releasing unprocessed exhaust gas from your exhaust pipe.)

How Long Can You Drive With a Bad Catalytic Converter

Would you expect a professional football player with an injury to still take to the field? No, right? So you shouldn’t take the risk either. Better safe than sorry.

In extreme cases, your car won’t even start because of a damaged catalytic converter.

And over time, your catalytic converter could become completely fused — requiring immediate replacement.

Still not convinced that driving with a faulty catalytic converter isn’t a good idea?

Let’s explain why you shouldn’t consider driving with a damaged catalytic converter.

Why You Shouldn’t Drive With a Bad Catalytic Converter

While driving, you are responsible for being careful on the roads and not causing harm to yourself, your passengers, and other motorists.

Driving with a faulty CAT is not safe.

Here are a few other reasons you shouldn’t be driving with a bad catalytic converter:

Your Car Could Catch Fire

When traveling long distances, a failed catalytic converter can cause your engine to overheat faster than usual, possibly causing your car to catch fire.

If you suspect you’re experiencing a catalytic converter problem but cannot get it looked at immediately — avoid trouble by preparing to stop throughout your journey to let the car cool off.

It’s Illegal

The Environmental Protection Agency (EPA) maintains tight criteria for catalytic converters. Suppose you’re driving with a missing catalytic converter and get caught.

In that case, you’ll be fined and unable to drive until you replace your catalytic converter.

In most cases, replacing your catalytic converter is less expensive than being penalized.

It’s Bad for the Environment

Without a functioning CAT, you emit harmful pollution from the exhaust system into the environment every time you drive. You may be asking yourself why you should care.

To paraphrase Starlord, you’re one of the people who live on Earth, so taking care of the environment is your responsibility.

Additionally, if unprocessed exhaust gas gets into your car, the harmful carbon monoxide can make you ill.

What Happens If You Drive With a Bad Catalytic Converter?

We’ve already established that driving with a bad CAT is illegal. So here’s what will happen if you get caught:

What Happens If You Drive With a Bad Catalytic Converter

You May Fail an Emissions Test

Vehicle owners must bring their vehicles for an emissions test at a specified date. A failed catalytic converter equals a failed Vehicle Emissions Inspection Test.

If your emission levels are too high, you have 30 days to fix the catalytic converter. You can then resubmit your car for a free retest.

You Can’t Renew Vehicle Registration

Failing the emissions test will result in a denial of vehicle registration. And if you’re thinking you can skip the test, understand that avoiding the test has the same result.

You’ll only be able to renew your registration once your exhaust fumes have suitable emission levels.

So, putting off replacing your catalytic converter can lead to you not being able to drive your car on the road legally.

You’ll Get a Fine

You can expect a $20 late fee for missing your appointed date for the emissions test by more than 30 days. Additionally, you’ll get a fine each time your vehicle is stopped and found non-compliant.

Every time you drive your car without passing the emissions test and get pulled over is a separate violation.

Remember that each fine will be higher than the previous one — making it possible to get multiple infraction citations before your registration is denied.

Multiple citations can ultimately become more expensive than simply replacing your catalytic converter.

Symptoms Of A Bad Catalytic Converter

Having a bad catalytic converter or driving without one can prove to be very unsafe and troublesome. it may not show signs in the immediate moment but you can be sure to have bigger problems down the road.

Lowered Fuel Economy

As capable as they are in lowering emissions, catalytic converters can also create a significant slump in gas mileage once they go bad.

Bad catalytic converters can create back pressure on the exhaust which decreases the fuel thermal efficiency of an engine significantly.

Sluggish Acceleration

Another problem catalyst converters most notably create is bad acceleration. The engine needs a nice flow of exhaust to operate efficiently and travel light.

But when carbon built in the converter leads to excess blockage in the exhaust it could result in poor acceleration.

You may try to floor the throttle but not get a proper response. In some cases, simply cleaning the device can help.

A Rattling Sound From the Exhaust

Any kind of sound coming from the exhaust is a signal for you to get your car inspected. Though sounds from the exhaust can vary vastly, from hissing, and pinging to thudding and wheezes, with each caused by a different reason.

However, if you hear a distinct rattling noise resembling that of a half-empty box of a jigsaw puzzle shaking, it could mean that the catalytic converter is damaged.

A broken converter can cause the honeycomb mesh interior to break or shatter producing a rattling sound when you make a turn or brake your vehicle as these pieces jostle around.

What Causes Of Catalytic Converter To Fail

Catalytic converters are built to last with most maintaining proper functioning for up to as long as 10 years.

However, their service interval is affected by a number of unavoidable factors like contamination, heat, physical damage, etc.


Older engines or the ones with overdue service tend to cause more rapid wear on the converter due to a number of reasons like excess burning of oil due to worn-out cylinder walls, sludge build-up, and worn valve guides.

A suboptimally functioning engine is known to cause faster wear and damage not only on the adjoining components but can have a far-reaching impact on the fuel management system causing damage to the catalytic converter through incorrect air/fuel mixture, timing, or misfiring spark plugs.

Physical Damage

The catalytic converter is made of lightweight ceramic material with a slim honeycomb frame. Though it is unprotected, outside of the ceramic material, It is wrapped in a dense insulation mat that not only holds the catalyst but protects against environmental damage.

However, the coat isn’t equipped to protect the converter against physical damage coming from off-roading, broken exhaust hangers potholes, side curbs, speed bumps, and others underneath your vehicle can strike the catalytic converter causing a catalyst fracture.

Once the ceramic honeycomb is fractured, the broken pieces jostle around breaking up into tinier pieces.

As a result, flow is hindered and the pressure in the exhaust system increases leading to heat buildup and loss of power.

Oil Or Antifreeze In The Exhaust System

The introduction of oil or antifreeze in the exhaust occurs when there is a spillage due to an improper fuel mixture. When these fluids make their way into the exhaust system they coat its entire interior with soot and thick carbon.

The growth of soot and carbon if unchecked can eventually clog the air passages in the converter’s honeycomb catalyst.

This further leads to two problems. Inhibition of the efficient expunging of pollutants and Increased backpressures of the exhaust due to the clogging of pores in the catalytic converter.

These two problems can further down the road result in a cascade of events that are destined to cause internal damage to the engine.

It can cause the engine to actually pull back burnt gasses into the combustion chambers which will progressively lead to inefficiencies in the burn cycles and generate excessive heat in the engine compartments.

Processing Of Leftover Fuel In The Exhaust

By design, the fuel is meant to be burned in the combustion engine with nothing entering the exhaust but fumes, the remnants of the thing powering your vehicle.

However, In case of an overpouring of the fuel due to a faulty fuel management system or sticking float, some amount of the fuel is sent to the exhaust unburnt and is left for it to process.

This continual burning of the fuel in the exhaust can overheat the converter beyond the threshold of operating temperatures and can be highly detrimental in the long run.

Short Trips

This is one of the rare causes of a catalytic converter going bad.

If you have a short commute to work or aren’t too fond of long drives, your catalytic converter might not be able to burn away the hydrocarbons it accrues with every drive as to get rid of the stuck pollutants, the device needs to reach a certain temperature where it is able to wipe out these contaminants.

In order to prevent this issue, you need not change your way of living but just an occasional 20-minute drive on the highway should suffice to the unclogging of the catalytic converter.

How Much Will it Cost to Replace A Catalytic Converter?

You should expect to pay between $500 and $2,200 to replace a failing catalytic converter in newer cars (newer cars have a more complicated CAT and are more expensive to replace).

A catalytic converter replacement in older cars will cost about $175 to $750.

The expensive metals used to make your CAT are part of what drives the high catalytic converter replacement cost.

However, don’t let the high cost of catalytic converter repair deter you from fixing a damaged converter.

Avoid opting for cheap repair alternatives like catalytic converter cleaner, as it might only offer a temporary fix.


It’s possible to drive with a bad catalytic converter, but it’s not advisable in the long run. The consequences of doing so can range from reduced fuel efficiency to more severe engine problems and increased emissions.

If you suspect your catalytic converter is failing, it’s best to have it inspected and repaired by a qualified mechanic.

Addressing the issue promptly not only ensures your car’s performance but also helps protect the environment by reducing harmful emissions.

You can technically drive with a bad catalytic converter, it’s not a wise choice. Take care of your vehicle’s emissions system to ensure both your car’s longevity and the well-being of our planet.

Related Articles

You may also find the following articles helpful: