How come my 2000 Infiniti i30t hesitates on acceleration? Could this be my o2 sensor

Infinite doesn't have an inertia fuel pump cutoff switch (turns off fuel pump in a rear end collision > 3 G's), that is Mazda and Ford.

Check for codes

One would assume you have done that
for the last 30 years

Google the codes & get an idea what system
has a malfunction

Then have a repair shop start all over & diagnose it properly

ENGINE HESITATES WHILE ACCELERATION

LOSS OF ACCELERATION

It can be fuel pressure issue or it's the problem with accelerator pedal or its clogged filters causing there.

There are many other possibilities. I suggest you to go through the list of help links mentioned below, these will help you to confirm where the actual fault lies: -------

Jerks and Hesitates During Acceleration?

http://technoanswers.blogspot.in/2012/07/2004-dodge-town-country-jerks-and.html

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Loss of acceleration?

http://technoanswers.blogspot.in/2012/02/loss-of-acceleration.html

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Headlights flickering and car hesitates to start?

http://howtobyme.blogspot.in/2012/02/headlights-flickering-and-car-hesitates.html

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How exactly the Vehicles Accelerator Cable works?

http://repairhelpcenter.blogspot.com/2011/11/how-exactly-vehicles-accelerator-cable.html

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How exactly Vehicles Accelerator Pump Diaphragm Works?

http://repairhelpcenter.blogspot.com/2011/11/how-exactly-vehicles-accelerator-pump.html

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2000 Toyota Avalon: Engine Lean Codes and Knock Sound on Acceleration?

http://whatisbyme.blogspot.in/2012/05/2000-toyota-avalon-engine-lean-codes.html

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2004 Toyota Avensis: Acceleration And Deceleration makes noise on Front End?

http://whatisbyme.blogspot.in/2012/05/2004-toyota-avensis-acceleration-and.html

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Wheel hop under hard acceleration?

http://technoanswers.blogspot.in/2012/04/wheel-hop-under-hard-acceleration.html

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2009 Chevy impala accelerator pedal sensor?

http://technoanswers.blogspot.in/2012/02/2009-chevy-impala-accelerator-pedal.html

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Nissan Pathfinder stalls and bucks on Acceleration?

http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-stalls-and-bucks-on.html

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Acceleration lag problem?

http://repairhelpcenter.blogspot.com/2012/01/acceleration-lag-problem.html

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These details will help.

Thanks.

Try cleaning the Mass airflow sensor and replacing the air filter. You can buy the spray MAF sensor cleaner from any auto parts store for about $6.00, ask the parts guy how to use it.

if you have an O2 sensor faliure you will have a code for it. in fact youe exterra doesnt have O2 sensors. it has A/F sensor or "air/fuel sensor" if it went bad, than you will have a code for that sensor. What is the code number that you have?? need to start there.

if you used a direct fit O2 it should not be giving you the code again unless the wires are touching near the plug, you got a defective sensor.
if you use a universal it may not read properly.

The throttle positioning sensor may have a inconsistant contact in a certain range. Generally caused by aggressive driving., seriously the pivots and other moving parts wear sooner because of indirect pressures at the throttle body.

You may be sucking in air into your fuel system due to a crack line or hose.It's hard to find a suction problem because it does'nt leak .Look closely at the supply fuel lines.

open the bonet, unlock the headlight cover latch remole the existing bulb thd replace with appropreate one.

have you cleaned the throttle plate? this is done by removing air intake hose and spraying out with cleaner and wiping it down open throttle and wipe off the butterfly and bore. this will usually cure a stumble.