Persistent high idle - 1600rpm. I have bought a new idle control valve, made no difference. Disconnected valve and plugged pipes, idle drops to 600 rpm. Tested TPS, even at ECU connector, no fault,(shows low ohms, touch accelerator and goes high). On starting engine, idle speed correct for about 1 minute and then abruptly goes to 1600rpm and stays there. Does this consistently as if there is a timer controlling it somewhere. Could the new idle valve be faulty? (not a Bosch but a substitute 0280140516). Have performed test at pin 2 of test button and I can hear the idle valve clicking as it should. I have run out of ideas!