electronic fault light/management lights on

[Rufnek20]

hi all, just bought a 172 cup fairly cheaply, 2nd day i had it the electronic fault light came on and it went in limp home 3000 rpm max mode, switched it off and problem went, until when ideing when warm at lights it seems to drop in revs and get a bit juddery then it went into limp home mode again with the fault light (idle control system?) after it did this 3 or 4 times the engine mangement (bottom right) light came on and has stayed on, anybody had this or knows wot it is? thanks, keith :S