Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

Or, hide this message: temporarily or permanently

IAC Valve Test






IAC VALVE SYSTEM TEST - (KOER)






Description: NGS Tester tests valve at Idle Air Control (IAC) settings of 0%, 20% and 80% duty cycle.






Results: Test fails if rpm fails to increase at least 150 rpm between 20% and 80%.