I have a '90 3.1L bird:
I just rewired my fan relay to the fuse box. Now, the car misses BADLY!! I just had a tune up (and fuel filter) done 2 weeks ago, and I haven't driven it but 30 miles or so!! Could I have knocked a wire somewhere to make it do this???

 

why would you wire a fan relay to the fuse box?

 

The electrical diagram shows 4 wires at the relay, one to the fan motor, one from a fusible link, one to the PCM, and one to the fuse box-which was melted (it looked like).

 

I would replace the relay.

 

Would replacing the relay help with the engine missing? Or is that just because the wire melted? Thanks for the advice-I will do that.

 

check to see what other damage the melted wire may have caused.
The fan relay should have nothing to do with how the car runs.
I would suspect that the melted wire either took out another wire with it, or caused a power spike that damaged your ECM or some other sensor.

The ignition-source wire going to the relay should NOT have melted unless the relay was shorted inside (bad relay). Fix that problem first, then find another suitable ignition source to run to the relay.

ODB