Hi all, I'm new here, have a few problems, questions

First of all, I've got a 1999 1.8 LX and just swapped the engines over due to a major fault with the old one, and often after stopping at a junction it revs itself to between 1500-3000rpm. It did this before I changed the engines over as I first thought it was the idle control valve but as it was swapped I don't see how it could still be happening?

Any idea?

Throttle position sensor.

tps or air leak from a vacum hose or throttle body seal or butterfly valve closed

[color="#0000FF"][size="5"][font="Times New Roman"]Hi welcome[/font][/size][/color]