My 2000 nissan xterra wont keep idle and it sputters when sitting. when i am driving it hesitates like it wants to shut off

Sometimes the computer will have an intermittant glitch. Wait to see if problem reoccurs and monitor it based on engine start-up/run conditions. ( I. E.) Hot, Cold, Under A Load, Idling, Cruising.

I have a customer with a 2000 Nissan Xterra 3.3 liter V6 with 180k miles. He stated that while driving on the highway the vehicle is fine. Once he exits the highway and drove on surface streets the engine stumbles, sputters and shuts down when he stops. The fuel pump is located under the right side rear seat. I removed the inspection cover to view the electrical connections. No problem there. I drove the vehicle for approx 20 minutes and it hesitated a little but not enough for me to come to a good conclusion. I needed the engine to heat up some more so I drove to Panda Express for lunch. I got my lunch to go, return to the vehicle and started the engine to eat while the engine idled. After my lunch was over I drove back to my customer's house. On the way God bless me with what I was searching for...the engine started to sputter. To shorten this story I replaced the distributor with a brand new assembly from AutoZone($233.65). Once I removed the factory distributor I spun it by hand and that's when I could feel that bearings were rough & worn.
Problem solved and my customer is happy.

make sure your air filter is clean and get some carb spray or throttle body spray and spray the valves and clean all the gunk off and hope that ur intake passages are not starting to clog up

You need a distrubuter. I would not us an aftermarket one because Nissans do not like aftermarket parts for some reason. But that is most likley it.

jason, im gonna bet the farm that you have a clogged catalytic converter, if you can get the vehicle to your nearest muffler shop most of them will test the converter for free. they simply drill a small hole in the exhaust pipe in front of and behind the converter and compare the pressure to see if its clogged, call ahead to see if they will test it for free, most will, hope this helps

clean the throttle body and change the maf. i had this problem hard to accelerate between 35 and 50 and would almost die when idling for a while changed mass airflow sensor cheaper on ebay 38 and i can of cleaner it too 2 cleaning after that it runs better now

Airflow sensor very well may cause it , and Throttle position and temperature sensor too.
All of it has to be checked with good scaner , that can monitor values and data from ECM.
You need to find a better shop.

missfire. check the plugs and change if necessary.

run scanner for trouble codes, some auto parts store will do this for free 

We are having the same problem. We are right now changing the crankshaft position sensor along with the intake and manifold gaskets.