My sons bonneville stalls after it runs for a while. I have replaced the cam sensor, found a lose ground on the fuel pump. these thing seemed to help some but it still does it.I have noticed that when it does it the voltage drops to around 12 volts. tonight I was cleaning the ground connections under the alternator. when I put it back together I had a good strong 14 volts but the alternator started getting real hot and the voltage started dropping. this is a new alternator less than a week old. I did noticed that the belt seems a little tight but I don't see any way to release some pressure from the Tensioner Pulley. I don't know if it has anything to do with the car dieing but the ABS system causes the tac and speedometer to jump around I have pulled the fuse to the ABS and it doesnt do it anymore.I tried to disconnect the unit but the car wont start with it unplugged. Anyone got any ideas where to look now I'm lost.

Could be a bad crank senor mine went bad and my car would just stall out when ever it got hot then it would fire back up after it cooled down. I got a new one put in and have been problem free no more stalls. Good luck and let us know what you find out.

Also you might want to look into this
https://www.gmforum.com/showthread.php?t=278980

Thanx trixster68 good information I'll try that. I did'nt think to look for a ground bus there.

When mine did that, it was a coolant leak onto the crank sensor. The cam and crank info gets out of sync and the ECM shuts it all off. YMMV

I had a Buick that would randomly stall out. Was at completely random intervals though- sometimes it would run 5 minutes, other times 35 minutes. Was the MAF sensor. Expensive bugger, but it fixed the problem after I tried everything else I could think of (crank sensor, TPS, maybe other things I can't remember). Just my $.02