Ford Fusion 2009 code P0491 make the air pump run vac line off valve and engine stalls

Question

when running the test on the air system to make the pump run by grounding the wire it runs with engine running and small vacuum line off the valve it has vacuum.
The issue is that the engine stalls when I run the test with my finger on the vacuum line. The code takes some time to come back on at least to turn on the check eng light on.
Is it a problem that the engine stalls doing the test? if so what does it indicate?

Answer 1

To begin with this type of test will set this code just by grounding the wire, its better to use a scan tool by  doing a KOER (key on engine running ) test. the most common cause is the air divertor valve you can remove it and blow through it, it should blow through easily with out that much resistance. in the direction of the airflow