P0420 code. Please help!

[AlexaG.]

Hi everyone. I just bought an '04 TR4 a month ago. Two weeks ago, I blew coil pack #5. I drove for about a week before having it fixed. It ran pretty rough but I was told I wouldn't hurt it by driving it. After having it fixed, my CEL came back on along with the VSC Trac lights. I took it back to my mechanic and he checked the code. Now this time it has pulled a P0420 code. He cleared it and the VSC Trac lights came back on about 2 miles down the road. Then the CEL light came back on about 20 miles down the road. Took it to Autozone and the same code came up. Autozone advised that it is most likely the 02 sensors. I cleared the code again and almost immediately the VSC Trac lights come on and then the CEL light comes on after about 20-25 miles. I reviewed some of the service records that came with the car and it appears coil pack 5 had been replaced twice within the last year. I am not sure if this has any bearing or not but I need help. My mechanic (who does it for a hobby) believes it is most likely the cat. How will I know for sure? Is there anything I can do myself to eliminate any simple things that may be causing the lights? It seems to be running fine after replacing the coil pack and using a can of Seafoam. I haven't even made my first payment on it! Aaargh! I have no idea what to do next.

 

[cabowally]

Been discussed in 20+ threads. Search on "p0420"


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[AlexaG.]

Thanks Cabowally. I had done a search before posting but didn't get as many threads as what just came up. Maybe because I am a member now. I am fearful I may have damaged my cat by driving while misfiring for a week. I was assured it would not do any damage.

 

[ldydoc]

I used to have a ranger that misfired like a SOB and it never really hurt anything. Lol. Then I killed it