Fast Idle not working

[altong0840]

hi everyone, i just wonder if my fast idle is not working, the car go up 1100-1200rpm when put in P gear and 500-700rpm when it in D gear, is it normal?

my car running a D15B4 twin carby engine....

please advice........

running the car without fast idle, nothing much feeling with but just want to fix it.....cheez