Having a problem with my Maxima. This started on a trip to Colorado and I thought it was a high altitude issue. While driving up into the mountains we started having problems with the vehicle shifting out of gear. We turned around and when we stopped at a stoplight it was very sluggish taking off. We stopped and checked a few things. Fluid looks normal, Air filter was pretty dirty, we banged it out and replaced it when we got to an auto parts store. Car ran fine the rest of the trip. Now we are having the same issues back in our low altitude home town. We tried pulling the codes, but apparently there are some issues with the power the port? We have one power port inside the car that has never worked and we were told that sometimes that's on the same circuit? I dunno. Wife says she thinks it's sticking in third gear, which would explain the sluggish take off at stop lights. Thoughts?
It does sound like a computer related issue. You need to have the OBD2 port checked to see if it can be repaired. Hopefully. That will give you direction to the problem. Without that, it becomes a guessing game.
Just for the heck of it, check fuel pump pressure to make sure it is within spec and check to make sure the catalytic converter isn't plugged. Either could cause the vehicle to be sluggish.