I've a 1997 A4 b5 adr 1.8 that's idling high from 1400 to 2000 , up , down & so on
 

Howdy everyone , I've swapped over the old engine for the same 1.8 ltr ADR with 100k less kms on the new one(out of an 1996 A4 ADR AWD quattro sedan , having to put the old flywheel , clutch plate & thrust bearing onto the new engine i was putting in , I also exchanged the whole steering rack and put new engine mounts in front and back , all went well but 1 electrical connection I can't find where to plug in. It's in the same harness that the 2 small wires connect to the engine just above the oil filter , i think they must be the oil temp and pressure . The one that's still not connected has 2 prongs and is a plastic encased(black & purple) female. It's got me buggered where it goes but has enough lentgh to nearly reach the starter motor , definitely the gearbox or even the back of the alternator maybe , anyone whom could help with this would be great. It also has an idle problem , when it's cold , it's idling fine but once at running temp of 90°C , it sits on 1400rpm rising to 2000rpm and back down to 1400rpm and up again to 2000rpm & keeps dipping and rising continually, I've cleaned the whole throttle body with carby cleaner but still doing it , any suggestions would be awesome , thanks.