Bad Catalytic Converter: Can It Cause a Car To Stall? [Explained]

The U.S. Environmental Protection Agency (EPA) has set standards to bring down levels of car pollutants, and the auto industry has responded by developing new emission control technologies.

A catalytic converter is an emissions control device that converts toxic exhaust gas into less harmful substances. It’s a crucial part of the car.

When the cat gets clogged and fails, it leads to emission problems and potential safety hazards. Catalytic converters are especially prone to breaking down because they heat up very quickly and can be damaged by dirt on the ground.

There are many signs that indicate whether your catalytic converter needs replacing- You can start by checking your car’s system for leaks or warning lights. check out our blog for more info.

Table of Contents

Can a bad catalytic converter cause a car to stall?

Yes, a bad catalytic converter can cause your car to stall. It may cause the car’s engine to stall when usually, the engine starts without any issue, however, it stalls once you press the acceleration pedal. This is happening because a bad catalytic converter does not let the engine to get sufficient air intake, and if it does not get enough, then your car will stall.

Can a bad catalytic converter cause a car to shut off?

No, a bad catalytic converter won’t cause a car to shut off, the reason for that is that the catalytic converter is not an ignition system and it doesn’t contain any functionality that can stop a combustion engine from working.

What happens to a car with clogged catalytic converter?

What happens to a car when the catalytic converter goes bad? These are the 7 most common things:

  1. Check Engine Light – When the catalytic converter goes bad it will trigger a “Check Engine” light. This can not be determined just by looking at one though as there are many other things that can set it off such as an emissions problem or another sensor. 
  2. Engine Hesitation – The catalytic converter, when functioning normally, reduces the toxicity and unburned fuel of the exhaust, creating less work for the engine. When it goes bad this can lead to hesitation of the engine as well as a decrease of power.
  3. A Rattling Noise In the Engine – There can also be a rattling noise in the engine that may become noticeable under acceleration. This is due to the deteriorated catalytic converter bouncing around inside of the exhaust system.
  4. Fuel consumption – If it is bad enough, the catalytic converter will actually restrict the flow of exhaust as well as reduce its effectiveness as a converter. This can cause increased fuel consumption and poor gas mileage.
  5. Your Car Jerks Forward – If the catalytic converter has gone completely bad it can eventually allow for raw fuel to flow into the engine. This causes jerking forward when at an idle or slow speed and can damage your engine if left unattended.
  6. Engine Misfires – If the catalytic converter isn’t doing its job of filtering exhaust properly it can cause engine misfires which in turn causes poor acceleration and difficulty getting up to speed.
  7. Car will not start – If the catalytic converter has completely failed it can cause your car not to start. The unburned fuel can flow through your exhaust, back into the engine and damage the oxygen sensors which are essential for the car’s computer to determine how much fuel needs to be added to keep it running smoothly.

Can a catalytic converter unclog itself?

Yes, a catalytic converter can unclog itself once you add a high-quality catalytic converter cleaner into your gas tank and run it through your system in high 2500-3000 RPMs for about 5min.

Can a clogged catalytic converter cause rough idle?

Yes, a clogged catalytic converter causes rough idle, because when this part is clogged, it doesn’t allow enough oxygen into the combustion chamber. As a result, the engine has to work harder.

How long can you drive with a bad catalytic converter?

There is no time limitation of driving when your catalytic converter has failed. However, it will have an effect as described earlier.

Does removing catalytic converter damage engine?

No, removing your catalytic converter will not damage your engine per se, however, you might damage your downstream and upstream o2 sensors and you may experience low-end torque loss. 

What OBD-II Trouble codes will a bad catalytic converter cause?

The common OBD-II Trouble codes for catalytic converts failure are:

Codes P0420 or P0430.

  • P0420 is a diagnostic trouble code (DTC) for Catalyst System Efficiency Below Threshold (Bank 1).
  • P0430 is a diagnostic trouble code (DTC) for Catalyst System Efficiency Below Threshold (Bank 2).

Can I hit my catalytic converter with a hammer?

Yes, you can hit gently the catalytic converter with a rubber hammer of mallot in order to figure out whether there are any loose parts inside the cat.


In this blog post, I wrote about a catalytic converter that fails, its symptoms, and answer the main questions many drivers are asking: “Can a bad catalytic converter cause a car to stall?”“. So, the answer is yes. It will happen usually when you press the gas pedal.