If your engine is idling too high, then check the following items:


Idle control valve


Check for moisture in idle control valve plug. If moisture found, dry and clean plug and add small amount of WD40.


Check the idle control valve is not stuck and dirty. Remove and clean.


Wiring looms


Check for moisture in black connector in engine wiring loom.


Check for moisture in white connector in engine wiring loom.


Check for moisture in deutsch connector where engine harness joins main loom.