How do I know if my Honda has a bad catalytic converter?

If your Honda is experiencing performance issues or failing emissions tests, it may have a bad catalytic converter. Catalytic converters are essential components in a vehicle's exhaust system, responsible for reducing harmful emissions. Knowing the signs of a failing catalytic converter can help you address the problem before it leads to more serious and costly repairs.

Signs of a Bad Catalytic Converter

Here are some common indicators that your Honda's catalytic converter may be failing:

• Reduced Fuel Efficiency: A malfunctioning catalytic converter can cause your Honda to use more fuel, resulting in decreased fuel efficiency.


• Difficulty Accelerating: A blocked or damaged catalytic converter can restrict exhaust flow, making it harder for your Honda to accelerate.


• Failing Emissions Tests: If your Honda fails an emissions test, it could be due to a problem with the catalytic converter.


• Unusual Exhaust Sounds: A rattling or metallic noise coming from the exhaust system may indicate a problem with the catalytic converter.


• Check Engine Light: The check engine light may illuminate if the catalytic converter is not functioning properly.

If you notice any of these signs, it's important to have your Honda's catalytic converter inspected by a qualified mechanic as soon as possible.

Diagnosing a Bad Catalytic Converter

To determine if your Honda's catalytic converter is the source of the problem, a mechanic will typically perform the following tests:

• Visual Inspection: The mechanic will visually inspect the catalytic converter for signs of damage, such as cracks, holes, or discoloration.


• Backpressure Test: The mechanic will measure the backpressure in the exhaust system to see if it's within the manufacturer's specifications.


• Emissions Test: The mechanic will conduct an emissions test to check for excessive levels of pollutants, which could indicate a problem with the catalytic converter.


• Diagnostic Scan: The mechanic will use a diagnostic tool to read any trouble codes related to the catalytic converter.

Based on the results of these tests, the mechanic can determine if the catalytic converter needs to be replaced or if the issue is caused by another problem in the exhaust system.

Replacing a Bad Catalytic Converter

If the catalytic converter is indeed the problem, it will need to be replaced. This is a relatively expensive repair, as catalytic converters can cost several hundred dollars or more, depending on the make and model of your Honda. However, ignoring a bad catalytic converter can lead to even more costly repairs, such as damage to the engine or other exhaust components.

It's important to have a qualified mechanic perform the catalytic converter replacement, as the job requires specialized tools and knowledge to ensure the new part is properly installed and functioning correctly.

Can you drive a Honda with a bad catalytic converter?

Running the car this way could reduce fuel efficiency and even damage some components. Rather than trying to drive a car with a missing catalytic converter, it's best to have it towed to a garage for repairs.

How long do Honda catalytic converters last?

ten years
On average, a catalytic converter will last for ten years or longer, although environmental and operational issues can cause it to fail prematurely.

What are three signs of a bad catalytic converter?

If you notice any of these symptoms, it's best to take your vehicle to a specialist for inspection.

• Rattling Noise.
• Blue Emissions.
• Reduced Engine Performance.
• Low Gas Mileage.
• "Check Engine" Light Comes On.
• Sulfur Smell from Exhaust.
• Failed Emissions Test.
• The Bottom Line.

How do I test if my catalytic converter is bad?

You can test a catalytic converter by using an infrared thermometer to check for a significant temperature increase from the inlet to the outlet, or by using a vacuum or back-pressure gauge to detect a restriction. Other signs that it may be bad include poor acceleration, a rotten egg smell, a rattling noise, or a check engine light. 
On-board diagnostic methods 
This video demonstrates how to use an infrared thermometer to test a catalytic converter: 30sHVAC Mechanic YouTube · Mar 25, 2023

• Infrared thermometer test: After the car has been running for about 15 minutes, use an infrared thermometer to measure the temperature before and after the catalytic converter. A functioning converter will have an outlet that is at least 50-100°F hotter than the inlet, indicating the catalytic process is happening. If the temperatures are the same or the outlet is cooler, it's not working properly. 
• Vacuum gauge test: Attach a vacuum gauge to the engine's intake manifold. At idle, the vacuum should be steady. When you rev the engine to about 2500 RPM, the vacuum should either stay the same or increase slightly. A significant drop in vacuum as the engine speed increases indicates a restriction, likely in the exhaust system. 
• Back-pressure test: A mechanic can perform this test by removing the upstream oxygen sensor and connecting a pressure gauge. The pressure at idle should not exceed 1 PSI, and at 2500 RPM, it should not exceed 3 PSI. Readings above these levels point to a clogged converter. 

Physical and sensory checks 
This video shows how to check for rattling sounds in a catalytic converter: 1mHVAC Mechanic YouTube · Sep 1, 2023

• Listen for rattles: Tap or gently bump the catalytic converter with a rubber mallet or your hand. If you hear a rattling noise, the internal honeycomb structure has broken apart and needs replacement. 
• Check for strange odors: A rotten egg smell coming from the exhaust can be a sign of a failing catalytic converter. 
• Assess performance: A clogged converter can restrict exhaust flow, leading to sluggish acceleration and reduced engine power. 
• Check for a check engine light: The car's onboard computer will often trigger a check engine light if it detects a problem with the catalytic converter's efficiency, usually indicated by a code like P0420. 
• Loosen the exhaust: As a quick (though temporary and potentially illegal) test, you can loosen the exhaust pipe connection before the converter. If engine performance improves, it confirms a blockage in the converter. Be aware that this may not be legal to do in your area and should be done only briefly.