How can i fix my 95 7840 sle?

My ford 7840 sle was parked up all winter before the winter it was driveing fine but some times it would stop moving and e45 started flashing on the dash i found wires burnt but got them fixed then it was fine a few months later it started it again but if you knocked it off and started it again it would be fine it started getting worse and worse then it was parked up for the winter but when i started it and started driveing up the road it only got a few yards and it started coming up e45 flashing on the dash and when you knock it off and start it again it is still flashing and beeping e45. Thanks.