1989 Chevy G20 conversion van. 5.7tbi / 700r4. recently the van has been losing electrical power randomly. this means when driving, it shuts off and for several seconds it has no power. after a few seconds the dash lights/blower motor etc all come back on and the van will start back up as if nothing happened. the problem seems to occur at low speeds when turning, coasting, or slowing down. does anyone know what could cause this or have any ideas? Thanks