Help!!! My Work Truck Is Dying

[plastikboy]

The other day I noticed a little hesitation from the throttle but I ignored it. Well, less than 24 hours later my truck is idling rough, pinging while driving uphill, it's stalled out once while driving at low speed and my SES lamp came on.
I think by coincidence this all took place after I changed my oil yesterday. I've changed my oil a thousand times and I used to work in a garage, so I can't imagine that changing the oil caused the problem.
So I think to myself: Throttle hesitation, pinging, rough idle and stalling... Need to clean the fuel system out. So I added fuel injector cleaner and it only seems to have made the problem that much worse. It might also be a misfiring cylinder, but I doubt in because the check engine light would have come on much sooner.
But I'm working my way on down the list. Check all wiring harnesses and connections, clean the fuel system, change spark plugs and wires. If any of those don't fix it, it's out of my hands and up to the ASE certified guys.

[nissandoc]

what year and engine do you have?

[plastikboy]

It's a 2001 XE V6 Crew Cab. It's the 3.3L naturally aspirated engine and it just turned over 70,000 miles. It's been abused (work truck...)

[Will2]

Sensors

[nissandoc]

first go to autozone and they will pull the code for free. that will at least give us a direction to go. did you check your air filter when you changed oil? when pulling up the air filter housing the resonator tube will sometimes come loose and cause an air leak on the back side of the airflow meter, causing running problems. with only 70k we normally dont see too many running problems with the v6's. let us know what code set the ses.