If I were you, I would change the whole throttle body + idle control valve with a scrapyard one. The throttle position sensor is integrated into the ICV, but you could have a fault with the TB itself. If you swap the lot, you know you've got a working unit. I got one for my 1999 1.2 brava a couple of weeks ago. £45 from Fiat Base in Birmingham (0121 3335296). I can definitely recommend them if you are anywhere near. They have a mountain of bravo/as in all the time and they certainly know what they are talking about.
Just be aware that there is a possibility that you will need to get it on the Fiat examiner to rezero and relearn the idle adjustment if you disturb any of these components. I had no problem, but the manual says differently.