Idle problems - phase 1 172

[mgoode180566]

Have a phase 1 172.

When idling for a while the rpm gradually starts to climb to about 2000 rpm and then fluctuates up and down. Blipping the throttle settles it back down to normal idle rpm < 1000.

Any ideas ?

 

[Russ_16v]

use the search function mate this is a common issue on the Ph1's

either idle control valve
throttle body sticking
throttle body spring
air leak