idle control valve on a tigra?

my 1.6 vauxhall tigra is reving up and down and the engine managment light came on.so had a code reading done. fault code idle control valve ive now changed this with a new one and the car is still doing the same thing it runs ok when first started but when the choke thingy goes of it starts to rev itself upto 3300 revs then back to 1000 for about a minute or so then stays at 3300