My idle/voltage problem was caused by a faulty mass airflow (MAF) sensor. As I mentioned in an earlier posting in this thread, the MAF sensor was replaced with a used unit, but this one failed as well a few weeks after installation.
Based on what I've read in this and other forums, the PCM cuts off the alternator field current below a certain engine RPM. The idle speed, at times, was low/unstable to begin with due to the defective MAF sensor, and turning the wheel caused a further drop in rpm due to the drag of the pump, resulting in low alternator output voltage.
Based on my experience in solving this problem, I would strongly recommend the purchase of a good scan tool, specifically one that can record real-time data values. Due to the voltage problem, I assumed (I know, I know) that this was causing the P0102 code to set and the unstable idle when it was actually the reverse. When I first recorded the MAF sensor frequency, it was normal, but then I noticed the reading intermittently dropping to zero, which I probably would not have found if it weren't for the recording ability of the scan tool. It was quite difficult trying to sort out cause and effect due to not knowing what the system was doing.
Since I already had a laptop, I purchased Scan XL Pro and their OBDLink Scan Tool, both reasonably priced. The latter is the cable that connects the OBD connector in the car to a USB connector on the laptop. It comes with basic software that can read DTCs, display freeze frame data and some component data values. The Scan XL Pro program expands the number of data values that can be recorded, and these recording sessions can be graphed so you can watch for trends and out of range values. Expansion packs are also available for specific makes that provide access to manufacturer-specific data.