My 97 STI 3 has a problem on tick over when it is hot it bounces from 500 - 1300 rpm ,have just looked under the bonnet to find the idle speed control valve to clean it out and I am unable to find it can any body assist or suggest what else would cause this problem.

 

I'm no expert but it could be the Mass air flow meter playing up (more likely?). Mine did that when it went.

 

Yep that what i'd say i was as well.
A normal crypton tuner will pick this up!!!

 

Chris,

open the bonnet and locate the intake manifold (it's quite hard to miss, it's the big red thing ). You will see a pipe from the intercooler to the throttle body, to the RIGHT of this, bolted to the BACK of the manifold is a small contraption with a plastic element at the top with 3 wires coming out of it. This is the idle speed controller. You can just pull the pipe off it and blow carb cleaner into it (make sure you do this in a clean environment as you will be allowing unfiltered air into the engine!).
The engine may try to stall (the air that is being drawn in is NOT metered so the ECU will not know to inject enough fuel).... this can be prevented by slightly opening the throttle by hand to allow metered air in.

You can also clean the MAF sensor by removing it from the vehicle and then using large amounts of brake cleaner (a carbon tetrachloride derivative). Do not touch the element, rather allow the brake cleaner to dislodge any crud. Allow the unit to dry and reinstall.... if you are lucky that will have fixed the problem, in any case the brake cleaner is highly unlikely to damage the MAF sensor, so if it still doesn't work then it's probably a duffer....

Cheers,

Pat.