oxygen sensor
 

where is and how do you replace oxygen sensor...the car is fine in neutral but in d,1 and 2 it runs like a sputtering duck....haven't tried changing plugs yet...did replace fuel filter...just started running rough all of a sudden...any help is appreicated

I'm assuming its on a 4 banger 2.3L, the O2 sensor is located on the exhaust manifold near the collector.

To get it out, you're gonna have to heat it with a torch and then crank it off with a good size wrench or ratchet or breaker bar.

oxy
 

YOU ALSO NEED TO CHECK THE TPS ALSO,

To get most oxygen sensors out you will need a 7/8" wrench or oxygen sensor socket with extension and ratchet depending on how hard it is to access.
Two things i can think of off the top of my head as your problem would be vacuum leak - if the problem goes away off idle and at higher rpm then it's probably a vacuum leak
Or it might be a misfire caused by bad plugs/wires or the waste spark 2.3's ('91+) have a notorius problem of the coil packs failing and causing the car to run on two cylinders temporarily or constantly depending on the conditions causing the failure.
Give us more information about your vehicle.