My 2001 Nissan Xterra sputtered when accelerating and then would go above 20 miles per hr. i got off the gas and it evened out then i gave it gas again and it accelerated normally. Then about 10 minutes later the same thing occurred. When I parked the vehicle and gave it gas it sputtered. Then i shut it off and started again and ran fine.

Tune up,fuel filter,did you change rotor?

Have an electronic evaluation carried out, it's quicker and in the long run safes you frustration and cash.

I find it dubious that a vehicle 13 years old only has 61 thousand miles on it. They are 4 cylinder engines and the belt needs to be changed every 65 thousand.

Chances are you need another speedometer, or send that one to a shop to have it fixed.

look at your coolant. if it looks like coffee or its thick or beige in color, than you need a transmission and radiator replaced. your radiator failed. the build in cooler to be specific, which caused your trans fluid to mix with cooant and trans got contaminated,. your trans is junk.need to replace it with new radiator. make sure to flush out your trans cooler lines also. some of the contaminated fluid gets trapped inside of them. you want to have the system clean as much as possible.

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.

Sounds like you have water in the gas. Are you in cold country? The whole country is right now. Anyway, if that is the problem, It could have easily come from the gas station, there tanks condensate too, Get a can of dry gas. If that is not it, get the code checker on there and see what it says, could be an o2 sensor, something in the air horn sensor. a bunch of things most people don't even know exist. hope this helps.

If the engine revs up while in drive and running at 40mph, your transmission is probably slipping. Try checking your transmission fluid level. If it is OK, I would get it by a garage to have them look at it to cofirm.

check vacuum diagram see if any pit hoes are in it also check hoses that connect to it are broken

had the same problem it was the u joints....if you get a vibration at higher speeds that will also be an indicater...on the 2005 exterras you have to replace the whole drive cshaft fortunatly min was under drive train warranty.