More likely to be the idle air control valve.
Remove and clean it and the throttle body. Use a new gasket on re-assembly.
If that doesn't work, fit a new idle air valve. You dont say what engine you have, but I suspect it is the £28 valve on this site-
http://www.autovaux.co.uk/LoadPortal.aspx?cnum=47&tabid=5&vnum=136
vaux
December 2009
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