Also, where is bank 1 oxygen sensor?

 

A bad cat, even if its plugged wont cause a misfire. A misfire, on the other hand, will damage a cat. On a 4cyl bank1 O2 is the sensor itself. However, there are two sensors. The sensor before the cat is called bank 1 sensor 1. The sensor in the cat is called bank 1 sensor 2. If you have a V6, bank 1 is near the firewall. Bank 2 is near the radiator.

 

A clogged cat that is creating any sort of exhaust back pressure can cause a misfire DTC to be triggered. However, that doesn't mean that the clogged cat came first though. As stated a misfire can also cause your cat to go south quick.

OP,

Post the Make, Model & Year of your Accord and a bit more leading info on this CEL code. That way someone will be able to tell you more about your issues. Is your Check engine light on or how is it that you know there is a misfire?

 

If your car was misfiring prior to your P0420 code, then you probably had other issues before your catalytic converter died.

Here are a few possible causes for a misfire;

• Fuel injector clogged, fuel leak, air leak
• Fuel injector circuit shorted/malfunctioning
• Spark plug carbon deposits, fouling or mechanical malfunction (what did your plugs look like when you changed them?)
• Ignition wires (you said in another post that you have already changed them)
• Distributor malfunction (worn cap or rotor, ignitor)
• Low cylinder compression (Have you ever had a compression test done on your engine?)
• Valve clearance out of spec (When was the last time you had the valves adjusted?)

 

No Ghost. A clogged cat will not cause a flucuation in crankshaft speed. The ECU moniters flucuations in crankshaft speed to determine if a misfire is present. A plugged cat may trigger other DTCs, but not a misfire.

 

Yeah not sure what I was thinking at first. Kind of obvious after I posted the possible conditions for a misfire and there is nothing in there about a clogged or restricted exhaust/catalytic converter. It's a good thing that you caught that

 

Thanks! Its hard to give on target diagnosis with such a vague question. Like you stated, It would have been nice if th OP gave us more details about his car or his actual concern.

 

It would have been even better if the OP would have stuck to his original thread that he started about his P0420 DTC and original misfire issues. I think he has 3 or 4 threads concerning these issues already.

Note to janek,

Try to keep all of the updates to your issues in one thread. If you replace something as part of troubleshooting an issue and something else happens. Make an update in your current thread don't start a new one. It will help other people help you quickly and more reliably.