Symptoms of a bad catalytic converter

What are the symptoms of a bad catalytic converter

Check engine light and P0420 or P0430 trouble code is a sure symptom of a bad catalytic converter

P0420 and P0420 trouble codes mean that your catalytic converter has failed the efficiency test. The test consists of rapidly changing the air/fuel mixture from lean to rich and back again and tracking the results with the pre-converter oxygen sensor and post converter sensor. That tells the computer how well the converter did it converting the extra fuel into CO and CO2 and how well it did in storing extra oxygen.

Hard starting and poor acceleration

When a converter overheats, the ceramic honeycomb and precious metals can melt and obstruct exhaust flow. In addition, excess fuel oil, or engine coolant coat the cells of the converter and restricts exhaust flow. That prevents the engine from breathing properly and that makes it much harder for the engine to start. You would experience this as the engine cranking but not firing up.

Poor gas mileage

Just like above, a clogged or partially melted converter prevents the engine from breathing properly, and that dramatically reduces acceleration and engine performance. If you notice that you have to press the accelerator pedal farther to get the same speed, that’s a sign you need to check out the converter.

A rattling sound coming from the  converter

An overheated converter can melt and break apart. Once the ceramic honeycomb breaks, it rattles when going over bumps. Tap on the catalytic converter with a rubber mallet. If it rattles, it’s damaged.

Impact damage on catalytic converter from road debris or parking lot curbs

The exhaust smells like rotten eggs

A dead converter no longer works to convert exhaust into non-polluting gasses. A sulfur or rotten eggs smell is a symptom of a bad catalytic converter.

If you suspect your converter is the cause, see this post on how to test a catalytic converter

See this post on how to clean a converter

©, 2020 Rick Muscoplat