I recently picked up a 1991 240sx from a friend of mine. He told me before i picked it up that he blew the head gasket in his old motor and had a shop put in another motor from a 1997 240sx. I dont know how much of this is true. But none of the gauges on the dash are working and i cant figure out why. I checked all the fuses and there fine so i have been looking for any loose wires. I saw these two wires unplugged in the picture below what do they go to?

 

I also found another loose wire around in the same area, it is a kinda sea green and looks to be a single wire into a small connector.

 

the black connector is your EGR and canister control solenoid valve connector and the other connector is your S.C.V control solenoid valve connector. (S.C.V = swirl control valve)

 

bingo!
these solenoids being unpluged won't cause your gauge problem. if what you were told is true then maybe the newer engine and ecu were not wired entirely.

 

How would i go about getting a wiring diagram that could help me with this thing?