Automatic choke problems

Automatic chokes do need attention sometimes. They become tired, gummy, springs and linkages wear or become weak.

A variety of methods have been employed to provide automatic cold-start enrichment and to arrange for it to be smoothly reduced as the engine warms.
In the early days of unfussy engines the methods were fairly crude but by the time of your car the automatic choke was quite sophisticated or complex.

I don't know the method used by Porsche but most cars used a flap to close, choke or strangle the intake and below is a much simplified description of a common method used on European cars.

Pressing and releasing the accelerator pedal before cold starting allows a bimetal spring to engage a stepped snail cam which increases the idle speed and at the same time closed the choke flap. Once the engine is started it would soon die from an over-rich mixture and so a small vacuum servo is employed to open the flap a small amount.
The bimetal spring is heated by an electric element and as it warms it will tend to open the flap and move the snail cam until the engine is warm enough to be able to idle, etc. without enrichment, typically 2 -4 minutes.

Yes, spring may have broken or maybe it just needs adjustment. There is a high idle cam that makes the card idle higher when the choke is closed or partly closed.