Whenever I have a high idle issue I ck the mixture setting. On old ones you have to use a Lambda box and later ones you can ck milliamps at the EHA. The reason I say to ck mixture first is that if someone leaned it idle will go up. Is your ABS light on also? Now after you know the mixture is right some idle control units have adjustments on them, if its original it probably doesnt. After that you are gonna have to get the manual out and ck for voltage at the unit . If the idle speed unit is bad it is best to replace unit and valve together.