Dephaser solenoid operation

[cartboy52]

Hi,

Does anyone know how much the dephaser solenoid should open?
When I check mine, it only opens by about 1mm.
Does seem much!

Disconnected, the car runs fine.
Connected it stalls when cold and runs lumpy.
I've has the dephaser pulley changed and it made no difference.

Just want to check if the solenoid is faulty before spending £80!

Thanks.