Can you commit suicide in a car with a catalytic converter?

Answer 1

Yes, they go almost as fast as cars without them.

OMG, that was so funny telecaster. But to answer the asker's question, catalytic converters eliminate 99% of the CO, carbon monoxide, in emissions. While technically still possible, unburnt gasoline would make the air too unbearable to breathe long before any risk of CO poisoning.