hey, i had this problem on my N/A starlet - i fixed it by removing the air filter housing so you can get to the throttle body. Then remove the ICV switch/magnet located just under the throttle body Try twisting the now exposed valve from behind this switch, if it's really solid thats your problem. To fix it, just spray some carb cleaner/brake cleaner etc/ into the hole just before the throttle butterfly until it's full, then start wiggling this valve back and forth until it moves freely, put it all back together and take it for a bit of a blast. Car might stall a few times and be a little unhappy but after 10 mins of driving it'll be fine and back to normal.