9 Signs Of A Bad Catalytic Converter In Your Car

Since the very first gas car back in 1886, cars have been improving at a steady rate. However, no car is perfect, and thanks to ever more rigorous emissions regulation, cars have become extremely complex and are increasingly more prone to catalytic converter issues. If you were wondering which are the symptoms of a bad catalytic converter, be sure to read this article.

Here are the symptoms of a bad catalytic converter:

  • Engine misfiring
  • Subpar performance
  • Rattling sounds
  • Rotten egg-like smell
  • Bad fuel economy
  • Check engine light
  • Failed emissions test
  • Black smoke is coming out of the exhaust
  • Your car stalls or jerks forward

Engine misfiring

Engine misfires are one of the most common symptoms of a bad catalytic converter and it usually indicates that your cats are overheating. The combustion process is greatly affected by a faulty converter and thus is unable to work properly.

Subpar performance

Another fairly prominent symptom of a bad converter is poor acceleration and overall poor engine performance. This usually happens if the honeycomb mesh inside the converter gets clogged with a significant amount of carbon residue.

Rattling sounds

As mentioned previously, the catalytic converter is lined with a honeycomb material which can sometimes break, and if it does, it causes rattling sounds, especially on start-up. It's always best to take your car in for a proper diagnosis in order to make sure that integral engine parts are not to blame.

Rotten egg-like smell

A rotten egg-like smell coming from the back is a definite sign of a bad catalytic converter. This smell is Hydrogen sulfide which is emitted because the cats are unable to convert it into less harmful particles. If you come across this issue, you are better off investing in a brand-new converter.

Bad fuel economy

If your catalytic converter is clogged, it means that your engine burns more fuel than usual. This can also happen because your oxygen sensor is unable to properly decide how much oxygen is needed thus the levels of fuel inside the engine are increased. If your fuel economy worsens at least by 10%, this is likely the issue.

Check engine light

All modern-day engines are equipped with advanced air to fuel ratio sensors called air-fuel ratio meters. These meters are designed to constantly monitor the balance of air and fuel inside the engine, and if the levels are unbalanced, it usually ends up in a check engine light coming on.

Failed emissions test

Failed emissions testing can also sometimes indicate faulty catalytic converters. This happens because your cats are unable to filter out all the harmful particles. If you do fail your test, be sure to exactly pinpoint the cause in order to fix it properly.

Black smoke coming out the exhaust

Probably one of the easiest ways to tell that your cats are at fault is if you come across black smoke coming from your exhaust. This can be due to many different causes, but more often than not the cats are to blame.

Your car stalls or jerks forward

If your catalytic converter clogs up significantly, it's bound to jerk your car forward. However, if your converter completely clogs itself, your car will stall because of a high-pressure build-up. Don't try and start the car up in order not to cause any additional damage.


FAQ Section

How much does a new converter cost?

A new converter usually costs between $1300 and $2000 depending on the car in question and the supply chain. Always try and find an original replacement part, even if it costs more.

Is it worth repairing a catalytic converter?

It usually depends on if your cats are clogged or damaged. If they can be repaired properly, then it's safe to do so. However, if it's only a short-term fix, it's best to replace the cats.

How long does a catalytic converter last?

An operational converter should last at least 6-7k, but most of them are good for up to 50k or even 100k miles. In other words, 5-10 years is to be expected.

Is unleaded fuel necessary?

It's essential that you use unleaded fuel, otherwise, your cats are bound to suffer at an earlier stage. This means that your cats will be under less stress during their lifetime.

What happens if I don't fix my converter?

If you don't fix your catalytic converter, the pressure will build up to a dangerous level, which usually results in complete engine failure.


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