1996 Ford Contour Engine Management System Short

I replaced the fuse for the engine management system with a fuse that was to large and some thing shorted out. I could smell burning wire or some thing like that. The car had no power at all. This problem was the ignition switch fuse in the fuse box in the engine compartment. The car starts fine now. Now when this fuse is replaced and the ignition is turned on the fuse goes bad.
the description for this circuit is the engine management system it is number thirty on the fuse box under the dash. This circuit takes a 7.5 fuse I used a thirty fuse witch caused the problem. This circuit has the temperature gauge and the heater blower motor on it ( I think the electric radiator fan is in the circuit too). This fuse has perotically burned out and been replaced with no problem but this was with the proper fuse. I have been slowly getting this car together. The contour has run ruff and would stall at time when in drive since I have had it. I replaced the timeming belt it ran better I replaced the og sensor it ran better plus full tune ups.
The odd thing is the car is running the best since I have had it since this short occurred. The dash lights seem to be dimmer than usual when the head lights are on.
I replaced the ignition fuse and have checked all the fused and relays in the engine compartment and under dash fuse boxes they are either good or show no signs of burning. I have checked the wires under the dash for burning and there is no obvious signs of burnt wires.
is the PCM module the problem? If so why is the car still running? I am willing to take any suggestions.