Symptoms of a Bad Clogged Catalytic Converter

By | September 13, 2023

If you think you have a bad clogged catalytic converter, there can be several symptoms that point to a bad unit.

Common symptoms include low engine power, misfire, running rough, strange smell, and more.

Symptoms of a Bad Clogged Catalytic Converter

  • Lack of Power

  • When a catalytic converter becomes clogged, exhaust from the engine will have difficulty pushing out.

    This will cause the engine to work harder and have less power than it normally would.

    The engine needs to bring in fresh air to mix with fuel, burn, and then expel it out of the exhaust.

    When this process is blocked, the engine will have less power.

  • Bad Fuel Economy
  • Since the engine is working harder to push out the exhaust gases, it will get worse gas mileage.

    If there is a notable drop in MPG, the catalytic converter may be clogged.

  • Excessive Heat Under the Vehicle

  • The bottom of the vehicle may emit more heat than usual.

    When clogged, gasses will build up before the converter, which also causes it to heat up.

  • Engine Misfires or Runs Rough
  • The engine may misfire since it cannot expel the burnt gases.

  • A Strong Sulfur or Rotten Egg Smell
  • A strong sulfur smell, often described as a rotten egg smell, can emit from the tailpipe.

    If a strange smell is coming from the engine exhaust, the converter may be bad or failing.

How to Test if a Catalytic Converter is Clogged?

  • Use an infrared thermometer to see the temperature before and after.

  • There are several methods to test if a Catalytic Converter is clogged.

    One common method is to use an infrared thermometer and take heat temperature readings before and after the converter.

    If the converter is clogged up, the temperature will be hotter before than after.

    If the converter is not clogged, the temperature will be hotter after the converter.

  • Tap on the converter and listen for any rattling noise.

  • When a converter starts to fail and become clogged, loose debris can often be heard rattling around

    If you can hear a rattling inside the unit, it likely is failing.

  • Loosen bolts before the converter and see if there is a power increase.

  • Another method to see if a converter has failed is to loosen the bolts directly in front of it.

    A clogged unit will reduce engine power since the engine needs to work hard to push the exhaust out.

    If the exhaust can escape more easily, the engine will have more power.

Can a Catalytic Converter be Unclogged?

  • A cleaner can be used, which can have success in some cases.
  • If the Catalytic Converter is clogged, it’s best to replace it.

There are several cleaners on the market that can be used to see if the converter becomes unclogged.

It is added to the gas, and the vehicle is driven, usually on a highway or similar, and the engine is reffed up to try and blow out any debris.

The results can vary and will depend on how badly the unit is clogged.

A popular brand is called Cata Clean, which has varying success rates.

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Read Reviews Here for Cata Clean on Amazon
Cataclean 120007 Complete Engine, Fuel and Exhaust System Cleaner

Category: Exhaust General Automotive Repair

About Bob Thomas

Bob Thomas is an automotive mechanic with 30 plus years experience. He is a contributor to several publications and has written many articles on automotive maintenance and repairs. He also has created many auto repair videos on YouTube.

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