I have an 05 focus. when I start it up it idles like it should. when I press the throttle and let up the idle goes high. to get the idle to go back down I have to shut it off. checked for intake leaks... none got any suggestions.
Might be a sticky throttle cable or throttle body (TB) butterfly. Have someone push the gas pedal and you watch the cable at the TB. Does it snap back after they let the pedal go? Might also want to look inside the TB and watch the flap move, maybe it is sticking some? Clean inside of TB as desired.
Maybe the IACV? Removing the idle air control valve (IACV) is easy on the Duratec engine. Clean out the inside of it with carb cleaner or similar product. I also hit the inside with a tiny bit of silicon spray lubricant at the plunger rubber seal.
same thought but just undo the cable and rev by hand, i had a vac leak that i never found with either but fixed it by just twisting all the vac lines around, not sure about yours but the svt has very few lines, mine was the large one back right of the head