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

Knock Sensor: Testing and Inspection

1. Start engine and hold engine speed to 2000 RPM.
2. Check timing while tapping on the engine block with a small hammer.
3. Timing should retard momentarily while tapping.
4. If timing does not retard, check connections and/or replace knock sensor.