Q: My car has check engine light and got codes P0420 and P0302. I have changed spark plugs and ignition coil but still sputters?

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My car started sputtering and losing power so i figured it was miss-firing. I got the codes read from my check engine light and it came back with P0420 (catalyst low efficiency) and P0302 (cylinder 2 miss fire). I figured the catalyst is probably has bad gas in it from the miss fire so i changed all my spark plugs. It still persisted so I got a new ignition coil. It still sputters and lacks power, what should I do now?
My car has an automatic transmission.

Hi John. Thanks for contacting us today. I think the first thing you should do is read this article about the P-0420 OBD-II trouble code. In most cases, this code is caused by faulty O2 sensors or a Catalytic converter that is clogged with excessive debris. That is likely the root source of your problem. But you might want to have a professional mechanic complete an engine misfire inspection to help locate the actual source(s) of the problem.

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