GMC Envoy revving high

Our Envoy rpms rev with foot OFF the gas pedal but in gear. We have no idea what this could be. Any thoughts?

Suggest for more ideas you post your question as a new thread @southerngalrn05 . Scroll up at the top left on this page where it says “maintenance/repairs”? Click that, then click “New Topic” on the next page, at the top right.