Hi Jade, I would first look at the idle control valve they are prone to getting gummed up, its mounted on the front of the engine to the right of the bunch of black bannanas, remove it and clean it with carb cleaner, if that does'nt fix it next most likely cause's would be the airflow sensor, or the throttle position sensor both are in the plastic tube comming from the airfilter box
nigel
January 2008