pole mkuu.. IST inatumia throttle body mechanical ambayo inaendeshwa na cable.. but kwa ist because of design ya throttle body, kuna valve nyingine pembeni ya throttle body inayokuwa inawekwa kwa ajili ya ku control idle speed ya engine (silencer) hiyo valve inaitwa idle control valve.. ndan inakua ni valve (electric driven) inayo control kiwango cha hewa kuingia ndani ya injini pindi engine inapokua at idle state (ie kwenye P or N). sasa hii idle control valve because of carbon build up huwa inakumbwa na tatizo la ku-stuck open or close.. sasa hii valve iki stuck close, engine idle speed itakua chini sana na hata kupelekea injini kuzima, iki stuck open basi valve itapitasha hewa nyingi kuingia kwenye combustion chember na kufanya idle speed iwe juu.. (kumbuka hii valve pia ndo inayofanya gari ipandishe silencer juu na kushusha pale unapokua umewasha air condition)
kwahiyo kwa tatizo lako inaonekana idle control valve ya gari yako ime stuck open therefore inaruhusu hewa nyingi kuingia kwenye intake manifold na kufanya idle speed iwe juu.. ni very simple problem ambayo hata wewe mwenyewe unaweza kulitibu.. fungua hiyo idle control valve, chukua carb cleaner spray yoyote pulizia, ule uchafu ukitoka tu gari mpya.., na kama ukimpelekea fundi akusafishie basi cost isizidi Tzs 10,000.
Kwa watu wenye gari inayokuja na throttle body ya umeme hili tatizo halipo na likitokea mara nyingi utakuta mtu kasafisha ile throttle body.. so kama ni gari ya toyota na ina throttle ya umeme, ikitokea idle speed imepanda baada ya kusafisha throttle, usijipe pressure kutafuta fundi ashushe silencer, gari yenyewe itajishusha to appropreate idle speed after few days. (hii ni kwasababu ECU ita relearn new position ya throttle plate na kufanya micro adjustment until idle speed inafika to appropriate level designed for that specific engine.)