um CHILL 125 cc. Service Manual page 42

 Unstable idle
ITEM OPERATION
1 Check whether the air filter is blocked and whether the intake pipe leaks.
2 Whether there is carbon deposit at the throttle body and bypass channel.
3 Check whether the IACV works well
4 Check whether the fuel pressure is about 250kPa.
5 Check whether the injector is blocked.
6 Make sue using the right type spark plug
7 Check whether the cylinder pressure is normal
CHILL 125 cc. SERVICE MANUAL AND EFI DIAGNOSTIC
RESULT
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
NEXT STEP
Intake system maintenance
Next
Clean the TB
Next
Next
Check the IACV
Next
Check the pump
Clean or change the injector
Next
Next
Change the spark plug
Next
Check the engine
42