[Brian]

Thanks Dave. I used a multimeter, and the battery output was 12.4 volts and the alternator output was 14.6. I didn't drive the car or let it run before the test though. Now I went back and tested the alternator output again, this time turning on other equipment to increase the load with the engine idling. With one or 2 on, the voltage drops down to the 13.X range. With everything possible on, it drops down to the low 12.X range.

I also tried wiggling the crank pulley perpendicular to the rotation direction, and it didn't have any play. But maybe the belts are keeping it snug?

The idle isn't constantly smooth, though. It occasionally sort of shudders (short but gradual increase and decrease in vibration and noise), and a small voltage drops seems to be associated with that.

I tried getting an ECU code reading once it started doing that. The "check engine" light did one long blink followed by 2 fast blinks, and then kept repeating that pattern. Is that supposed to be interpreted as a "3" or a "12"?