right got in the car this morning (uk sti blob) started it up waited for the temp to rise then drove 5 mins away to my friends, whilst waiting outside the revs began fluctuating from a steady 700 then flick to 900 back to 700 then 900 it done this bout 5 times, its never done this b4, any theory as to y this happened any info would b much appreciated cheers people .

 

just had to get another idle control valve for mine as it started going funny a couple of weeks ago.first it started like yours is the revs where jumping from around 700 to over 1500 up and down but it kept going away and coming back over the period of 2 weeks, then started it one day and the revs just stuck at around 1500 also my engine check light came on.might not be the same problem as yours but if it gets any worse might be worth a look.

 

I had a similar problem on the RB5 and it turned out to be the throttle position sensor (I did clean the ICV first but it made no difference) - tickover is rock steady now.