Stalling, Idling Issues

The car: 2000 Camaro V-6, all stock, 56,000 miles on odometer, AOD.

The Problem: While driving in OD, vehicle will downshift by itself and back to OD on some occasions. Sometimes more than others.

Now in addition to that problem, my car idles very rough (drops below 1000 rpms) and sometimes stalls.

Check engine light says system too lean. Replaced 02 sensors but problem still persists.

Don't know where to start as I think that it could be a multitude of problems. Don't trust taking it into dealer these days. Any help will be greatly appreciated.

What specific code did you get? Have you checked for any vacuum leaks or exhaust leaks before the 02 sensor.

I had the code read by a handheld obd2 scanner and it indicated that the system was too lean. Code P0174, bank 2 oxygen sensor. The O2 sensors were not the problem as they have been replaced and the problem still persists. Is this problem related to my transmission problems too?

You could always try swapping sensor from bank to bank and see if the code follows. I would make sure there are no vacuum leaks, check the intake track coming from the air filter box to the throttle body. Check all of the vacuum lines such as the EVAP, EGR, and brake booster. Also, make sure you have good fuel pressure and that the MAF sensor is not dirty.

Yes, the first thing that I did was to replace the O2 sensors on both sides. When that did not work I cleaned everything from the throttle body to the MAF. I replaced the air filter also. I tried fuel injection cleaners and everything but the problem still persists. I am wondering if the idle air control valve is faulty. If that is the case, then it could be an easy fix. However, my biggest concern is the issue where my car downshifts by itself and back again over and over again. When I commute a long distance, it is very problematic. Any ideas what could be causing this? Thanks.

Seeing that the code is also specific to one bank, I would also check to make sure there aren't any exhaust leaks before the 02 sensor on that side.