You're running way too rich.




Peter wrote:
Newps wrote


Why was the pump on and why were you at full rich?


Because that is how it is when one lands.

I have done some test runs today and found that the problem can be
repeated if one quite decisively pushes the throttle shut - that drops
the RPM from 700 to about 500. It happens only when the engine is
warm; say CHT of 330F or higher. The mixture doesn't really affect it.

So it seems OK, but I might inspect the throttle linkage anyway.