reason is, that you have rose the idle rpm, by trying to adjust it higher.
its not possible to turn it higher! If you try, you have finally your symptoms.
unplug idle valve.
close the idle srew ( the right one, if you stand before the car) to 0.
idle should be around 600 ( very low, almost stalling)
turn right screw slowly open until idle is at 700. ( still to low)
plug idle valve in. Idle should now rise to 800-850.
its not possible to turn it higher! If you try, you have finally your symptoms.
unplug idle valve.
close the idle srew ( the right one, if you stand before the car) to 0.
idle should be around 600 ( very low, almost stalling)
turn right screw slowly open until idle is at 700. ( still to low)
plug idle valve in. Idle should now rise to 800-850.