P0420

[edldrummer]

So I just replaced my COPs and spark plugs on my '01 V8 and still seem to have a missfire problem when the car isn't at it's full running temp.
I've got a CEL light that says P0420 (Catalyst system below efficiency) on bank 1.

So I figure it's either an o2 sensor or a cat. I've only got a basic set of tools, what should I do to determine which?

 

[86markviilsc]

A fairly simple check is to switch the secondary O2 sensors and see if the problem goes to the other side

 

[jjcool00]

Swap O2 sensors from left to right and see if the code remains the same. If it does, then I would suspect cat (which I suspect anyway), if it changes to BANK 2, then its the o2 sensor.

Which plugs and coils did you use (brand)?

Did u correctly gap said plugs to 1.0?

What I suspect is that you have a failed cat, the symptoms resemble a misfire, but it's not actually a misfire.

 

[edldrummer]

Thanks for the swapping tip. I'll give that a try. I assuming we're talking about swapping out the sensor at the cats right?

 

[86markviilsc]

The sensor after the cat

 

[mlara1129]

If you decide to try seapping the sensor locations, I'd recommend taking your car to a reputable exhaust shop to have the sensors swapped if you dont have the right tools. The last thing you want to do is strip one of those sensors.

 

[Telco]

You can pick up an O2 sensor socket at the parts store, it will be the right size and will have a long slot cut down one side. Also, make sure to clean the threads and put new anti-seize on them so they will be removable in the future.

 

[RigsLS]

Try clearing the code first, see if it comes back right away. Run an STP injector cleaner through it.

 

[edldrummer]

I took it to a good local muffler shop. Turns out the cat was clogged. Had it replaced.