325 ix stalling and serging problems

Hi I have a 1989 bmw 325 ix .I'am having a hard time finding out why my car when I come to a stop and have my foot on the break for more than 30 seconds serges and then shut down .I can keep it running by giving more gas.I have swapped out and tried many different parts(idle valve,computer,maf,fuel filter,distributer cap and rotor,adjusted valves,o2 sensor).My car is a automatic also .A few mechanics told me that it is electrical and I tend to agree because my on board clock keeps losing the time and I can hear the engine through my radio .

Please help if you can.