After changing the coolant temp sensor and still getting a weak cold start, I started looking at hoses. 

The breather hose on the front of the engine has a big split in it, so needs changing. Same thing happened with my Mk1 Focus.

A few questions - based on the attached images, which is the right breather hose? Is it the T or the bendy one? My thinking is it’s the bendy one  

Will I need to remove the intake manifold to change the hose? Looks tight. Couldn’t even see where the hose ends. 

Anyone done this job? Any tips?

I don’t know the exact answer, I had a mk1 focus on which it split.  Whilst the inlet manifold hinders access greatly I managed to wrap insulation tape round the hose where split. It was fine after that. 

14 hours ago, hazbaz1984 said:

A few questions - based on the attached images, which is the right breather hose? Is it the T or the bendy one? My thinking is it’s the bendy one  

Will I need to remove the intake manifold to change the hose? Looks tight. Couldn’t even see where the hose ends. 

I think it's the 'plain' one without the T piece.  Would recommend following it to double check though.

Comes out of block just underneath the 3rd inlet port.  And enters the manifold just to the left* of the throttle body & MAP sensor.  

*(Left as you're standing in front of it)

So, have taped the split up for now. Had to remove the inlet air hose (I don’t understand how they got that clic-r clip on the throttle body, as I can’t get it back on), alternator and MAF plugs to get access to the hose. 

If anything, the stalling and idle issue is even worse than it was.

Any other ideas about what might be causing the engine to start and idle so poorly?