1994 Geo Prizm My Geo Needs help!

Engine Mechanical problem
1994 Geo Prizm 6 cyl Two Wheel Drive Automatic 194xxx miles

My name is Jill and my dad and I have been trying to figure whats wrong with my geo prizm. I was driving it 6 wks ago and everything shut off completly and couldn't get it started. We repaired the brakes, fuel pump, cap and roters, filter and a few plugs and I took it to a michanic and he had it for a month and a wk and couldnt even figure out what was wrong with it. We got it now to start and it'll run fine but untill you stop at a stop sign it'll die everything will shut off. We are stumped and I hope you can help.

ps. Hope to here from you soon
thankyou