What causes circuit on idle control valve to reverse its polarity?

this is for 1991 toyota MR2What causes circuit on idle control valve to reverse its polarity?
pull your iac valve out take some carb cleaner pull in and out a couple times spray again then have some one cycle the key while spraying it see if it moves in and out if it does reinstall if not replace the sticky junk you just cleaned will cause the iac to mallfunction by not letting it cycle properly a nother trick i do is the hole it came from spray it down good to take a knife or something like that and get the gunk from the hole good luck