So, started it and held the gas down enough to keep it over 1,000 RPM for a bit, then let up; tried to die, gunned it and kept it running, held it around 1K for a little while longer; repeated a few times, until it would stay running on its own.
I'm wondering if this has anything to do with the sudden drop from 50-ish to 30-ish over the past 24 hours.
Not sure if the computer forgot the idle settings because the battery died, or what. Maybe the computer was using "known good" values the first time, and I shut it off before it could finish learning, and when I restarted it tried using the incomplete learned values. I don't know.
If this keeps up, though, I'm going to have to get rid of the Jeep, and I don't want to do that. But I need a reliable vehicle, not one that may or may not work depending on its temperament; I'm so pleased with the fact that it waited until I was "work at home" to become cantankerous that I'd hate to have to sell it.
MAP sensor is about $50 from Rockauto. TPS is about $25. No idea if the engine is throwing codes and no way to check it.
I suppose I could try cleaning the idle air control valve first.
It wasn't running badly, either before or after it started acting up. It just wouldn't idle until after I'd run it at 1k for a while.
After dinner I'll go back outside and try starting it again, see what happens. *sigh*