Chevy Astro Van 1995 RPM goes Very High when in shifted into drive.

I have a Chevy Astro Van 1995 that RPM goes Very High when in shifted into drive.
Any comments appreciated.

The idle is controlled here with an IAC, or idle air control. If another air source is present, the additive effect, with fuel delivery can cause excessive idle speeds. It is also possible for the throttle to stick off idle, causing a high idle condition. Food for thought. Ray