As if my xterra knew I had a few bucks saved up, it started acting stupid.
2002 SE/SC
93,000 miles
Auto
On a cold start, the thing runs fine. If it gets warm and I turn it off for a few minutes and restart it, there is a misfire for 20-30 seconds and then runs fine again.
I have pulled the codes from the ecu:
Misfire cylindder#2
Cat fault bank#2
I know a misfire can ruin a cat, but can a bad cat cause a misfire? If not, what could cause a misfire that only happens for a few seconds after a warm start?
Any ideas would be appreciated.

93,000 miles,... gotta ask, have you replaced anything recently? two ways to look at that question, one way, is you changed the plugs and maybe put a bad one in, or messed something up,.. the other way, is that you have NOT changed plugs, and they are going bad. Just some thoughts.......

plugs, wires, timing belt kit? Not saying that the problem IS with either of those items, but if they are all still original and you plan on keeping it much longer, they are things to consider. Its is suggested to replace the Timing Belt at 105K miles, OR seven years, and when doing the belt, it is recomended to replace all the other goodies that are in there at the same time, other belts, water pump, etc.. (search for TB replacement on the site, or check out all that comes in the TB Kit from Courtesyparts.com. I think the plugs claim to be good for 100K, my plugs showed heavy wear at around 85k. you could always have the codes cleared and then check them again to see if it comes back as the same Cyl misfire code.

If my understanding about the cats is anywhere close to right,.. and I by no means know much about them, Just some info I have read... a bad cat, COULD cause a misfire, a bad cat could cause the ecu to act differently with the amount of fuel it would send to the engine, either running to rich, or too lean depending on the conditions.

someone who knows more, may confirm or correct what I say, but this is at least food for thought for you. some things to check first, look at it this way, If you are planning on keeping it for some time yet, you can replace plugs and wires, and do the T-Belt kit for about the same cost as replacing a cat, and If you havent replaced any of those thing, then you will have to shortly anyway.

Nothing has been changed recently, and a bad plug makes sense. I just have never seen a bad plug start working after warming up.

Also check to see if your o2 sensorsae tight, I had one that worked itself loose and would let enough fresh air to thrrow the cat code.

Not lokely but it is a possability.

With that many miles on it and a misfire, it's time to do a tune up. I'd bet the problem is a bad plug wire. I'd replace the plugs, wires and if it has them (not sure for that year) the cap and rotor button. I'd reccomend using Nissan parts for the tune up.