[wibilly]

i would guess its the wires from the pic up coil under the plate where the modual mounts they flex as the vacume canister alters ignition timing and over time they fail. i've had this problem before. a new picup coil and you should be good to gobut as said before a complete distributer with all parts right down to cap and coil can be had for about $70. if i rember right to change the picup coil the gear must be removed from the bottom and shaft pulled out from top to get the plate off