I'm a missionary in Tanzania East Africa. I use my 2001 Land Rover Discovery II to reach the unreached people groups in the bush of Africa. I have a problem with my Land Rover, as soon as it reaches operating temp, the Idle will drop to 640 Rpms and some times stall. I check the hawk eye Computer, and it brought a code (32) p0505 blocked Isc valve. Could this be the problem? what is a Isc Valve?