Engine speeds up and down. on 2001 Ford Mustang

Engine seems to speed up and slow down even after it warms up. I read somewhere that something dealing with the throttle body needed removing and cleaning with carburator cleaner. Can anyone explain exactly what needs to be done?

1 answer
the deposits at the throttlr plate can cause this kind of issue
more than that, the idle air valve is a more common failure. have it check for operation.