How is the idle speed controlled on my 1984 4.1 sedan deville?

The idle is high which is making the car push on when I brake. The other day when it was wet the front wheels locked up and I carried straight on across a road junction. Not good, I need to get this sorted!

I suspect that the Throttle Position Sensor (which I would think your '84 has) needs to be replaced. However, it could be related to something else, including a vacuum leak.