91 lx gauges don't work

This is a recently bought restore/salvage car (don't care as long as it runs and saves gas). The gas, rpm, temp gauges, indicator lights don't work yet speedometer, mileage, dash lights work. It should be worth mentioning that the radio cuts in and out so i unplugged the radio (not sure if it's the radio unit or the electronics in the car). I checked all the fuses and they seem to be fine. When i was checking the dash fuse box, i noticed at least one wire that was connected to two other wires with duct tape.

i'm not sure what to look for or what to do. can someone tell me what i should do to fix this problem? should i check the wires? i've got the haynes manual with wire diagram but what am i to do with it? do i simply trace each and every wire? what should i be looking for when i'm "checking" the wires?

also, there's a gray wire (eminating from the engine wire harness) that's been cut off from what seems like the AT solenoid valve (i'm guessing to cut out the CEL light). the gray wire is not long enough to reach the AT solenoid valve and i'm not even sure if it should be connected. will replacing the AT solenoid valve solve this problem? will i need to get an engine wire harness form junk yard?

more importantly how can the car be running and acelerating without the AT solenoid valve disconnected? is this harming the engine and gas mileage?

other then that the car runs.