Rep Power: 0

Hi my Honda Civic 2000 Ex (stick shift) check engine light came on and the mechanic said it was a 505 code which was an air sensor so we replaced that.
I drove the car for a few days then the check engine light came on again and now the code is a 420 catalytic converter. When I drive the car it feels like it is about to stall. It jerks back and forth and won’t go right away but it hasn’t actually stalled yet. My mechanic said he can get an after market part with labor and estimates $500 for repairs for the catalytic converter. Has anyone been able to drive with a bad converter for a few weeks without it actually stalling? Also does this sound like he made the right diagnosis and will solve the issue? Thanks for your help!

 
Rep Power: 512

Depends on the reason for catalyst failing. Clogged cat, you'll run into issues. I had a 420 code on my 2002 and mine was fine (e.g. ran like it was supposed to), and mine threw the code because it was a high flow catalytic converter. I solved that with an O2 simulator. Sounds like yours is a bit more than the cat not doing it's job very well. Either that or it's causing enough of an issue to throw your AFRs off by a lot. That also is not a good thing.

 
Rep Power: 0

So are you saying replacing the converter may not solve the issue?

 
Rep Power: 512

I was more responding to "Has anyone been able to drive with a bad converter for a few weeks without it actually stalling?"

As far as diagnosis and what have you, the only thing your mechanic (and us) have to go off of is that P0420 code. Only way to fix that is to replace the cat. Why your car is kinda bucking and almost stalling is beyond me. Can be a myriad of things. Could be AFR related. Could be as stupid as a vacuum leak. Could be something else. The only thing we can really help see what you can solve is that P0420 code.

 
Rep Power: 0

Ya that’s what I’m worried about don’t wanna keep putting money into it and not solving the issue at 272k miles...

 
Rep Power: 367

if the cat is clogged, it's like having a diarrhea but someone plug your exit pipe.
you would buck and jerk as well. And eventually stall

 
Rep Power: 512

Could do a test. Disconnect the cat and let the exhaust flow pre-cat. It'll be loud. You'll likely feel a loss of power. Does it still buck and jerk? Does it still feel like it's gonna stall? No? Reconnect the cat, do the symptoms reappear? It's your cat. Symptoms still there? It's not your cat. Well, for those symptoms, at least.

Basically, what that does is take the catalytic converter out of the equation. That's the only way I can think of to test if the cat is the perpetrator. If anyone else has any ideas, post up

Question.. Is your check engine light blinking?

 
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No check engine light is not blinking. Thanks for the info.