Hi, My mate has a v3 wrx with a very strange idle poroblem. Every now and then it has a high idle 1300rpm?
I checked the ecu for any fault codes but nothing showed up.
Checked for air leaks to no avail. I was thinking maybe the idle control valve?
The other thing is yesterday when it was doing it i shut off the ignition and it made a solinoid noise for about 5 seconds? Sounded like the b/c only much faster??

Anyone?

 

Most likely it's the ISCV at fault, especially if the revs seem to 'hang up' as the engine returns to idle, altough normally it will show as fault code 24.

You can try removing it, cleaning with brake cleaner and sparingly re-oil the blade with WD or similar.