Thats what I thought

Sorry yes, you saw it first. This has to be it. Let's hope.

something like this.....

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1970 Mk2 Cooper S under restoration

Tomorrow if I can remember , I am going to run my car and take the cap off and see what happens and report back
Cheers

OK , couldn't wait till tomorrow
Engine at idle roughly900 / 1000 rpm . no choke .still not up to temp
remove oil cap and idle speeds up as now extra air being allowed into the crankcase and then fluctuates but does not stall
in my non educated , non qualified , self taught backyard tinkerer , I would
as a test , start engine , remove oil cap at the same time some one pulls the choke , if the engine still runs with the choke out , your carby mixture is to lean or you PCV has a problem .
Please note I am not an expert and don't claim to know everything , just saying what I would do

I reversed the PCV lid but not difference.
Thank you for all your inputs.

It turns out to be a leak in the power brake hose.

Have you checked the one way valve to the brake booster?

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timmy201 That's my next job but for now the booster is not going to be fitted.

Hi Cooperess

Sorry a bit late catching up on reading this engine stall matter.

I had the same issue at one stage with my Mk 2 - it turned out to be a pin hole in the power booster rubber diaphragm.
Replaced the diaphragm and no further issues.