I have a similar problem myself. We came up to Wisconsin for summer camp and when we tried to crank up the truck, it was hard to start and voltmeter kept wanting to drop at low idle, but at hi idle it was fine. We had the batt checked at walmart and replaced (OE battery) and everything worked fine. Then, the other day when we tried to go somewhere for camp, it started acting up again. After running it for about ten-fifteen minutes, it seems to do fine. I can stop and go into a store and it seems to do fine when I come out and try to restart. I'll try the battery disconnect trick and see if that tells me anything, as well as using a voltmeter.
Thanks in advance,
I live in my own little world, but it's ok.....
they know me here.
-2000 XLT Super Cab 4D 4.0 OHV 5-speed
Hidden Sub 'Mod'
-1959 VW Karmann Ghia Convertible 1776cc Dual 40 IDFs
1996 Suzuki Katana GSXF 600cc Gas Mizer