I'd check your idle IAC (idle air control) valve on the back of the throttle body. Could just be carboned up, or froze. Froze means replacement. BTW you can't move it when theres no current going into it so don't try.
I know theres a voltage test you can do...google IAC test and the info should pop up. A bad IAC doesn't always pop a CEL until the a certain number of failures are counted.
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