wd40 should never be used, because,as any intelligent person will tell you,it evaporates in a few hours,and leaves a grease like residue....making the valve sticky.

a thin oil is best.

and the best thing to clean them with is a solvent based cleaner like carb cleaner,as it evaporates away to nothing,



but its fact that 90% of so called iscv problems,are not directly related to the valve itself....people seem to think a surging idle is a iscv fault....but that normally means the valve is working perfectly well,rasing and lowering idle......its an engine setup fault more often