172 Failing the "Idle Test"

[Randall45]

What are the implications of a 172's engine quitting after putting the throttle in idle. Is it more likely that the throttle needs to be calibrated (i.e. it is cutting of fuel flow)?

 

[Dan Thomas]

Carburetor ice. If it idles fine most of the time but not once in a while, look up the temperature and dewpoint at that time and see that the spread is small, and conducive to icing.

Dan

 

[Randall45]

What if it's fuel injected

 

[jjflys]

Known issue with 172R and 172SP. I have found leaning at 1200RPM to a 100RPM rise before taxi seems to help.

 

[Randall45]

Thanks guys.

Sounds about right. I asked and they said just restart and go.

But then what is SOP for the idle check. Pull it to idle, hear it getting rough, add power to prevent imminent shutoff?

 

[JHW]

What if it's fuel injected

Intake air leak

 

[flyingron]

It could be that idle mixture is set too rich. Usually more often shows up when the engine is HOT.

 

[zodiacflyguy]

If it was an older airplane, it could be obstructed idle air bleed