I have a 1999 Chevrolet Camaro with a 5.7 liter engine and a manual transmission.
It recently started idling high but only when coasting. If I slow down because of a stop sign or whatever and hit the clutch, it'll idle from 1400-1800 rpm. It will do this in neutral as well. The idle stays there until I come to a stop. It's fine while sitting still, it's just while coasting, even at slow speeds.
I had a check engine light on but unhooked the battery and when I reattached it the check engine light did not come back on.