What should I do if the neutral idle speed of Elantra taxi is high in 2005?

For the question you asked, it may be that the throttle is stuck or beyond its adjustment range due to carbon deposition blocking the idle channel, or it may be that the throttle shaft or idle motor is stuck and cannot return due to too much carbon deposition, which leads to the increase of idle speed after receiving oil. Many times, after cleaning the throttle, the idle speed of oil collection will rise. This is because when cleaning the carbon deposit, the carbon deposit solution enters the throttle shaft, causing the throttle shaft and the valve body base to get stuck. I hope my answer is helpful to you.