2006 Honda Accord Issues

[Drae]

I have a 2006 Honda Accord Lx 4 cylinder. I've been having some issues with it for the past couple months. I changed the alternator a little over a month ago and it was doing fine for a while. Then, a few weeks ago, it started to shudder pretty violently when I went to park it. I checked fluid levels later, and they were all good. I started it back up and it was fine. Then, it started having issues when accelerating to higher speed (around 60mph) and the check engine light would start blinking. So, I took it to a mechanic and they changed out the spark plugs and knock sensor and told me my battery was bad. Went and got a new battery and all seemed well, but then it would start shaking every now and again when started it up and the check engine light came back on. So, I took it back in and they ran the codes and said it was a code for the catalytic converter. They cleared the code and told me that I have any more issues, they'd look into a replacement catalytic converter. While I was driving, my car's check engine lightstarted blinking, again, and when I parked, it started shuddering, again, so I used an OBD scanner I got and the codes p0420, p0302, and p0303 came up. I talked to my dad about what was going on and he said he'd never heard of a catalytic converter causing a car to shake, so I'm wondering if anyone could give me advice as to whether I should get the catalytic converter changed or if there's a more likely cause for my car's symptoms?

Edited June 12, 2023 by Drae
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