Hi,

the idle behaviour of my V12 gets worse. On cold start it is idling too high (up to 1400rpm) and taking too long to come down settling at about 900rpm. When the engine is warm and I restart it, the idle speed is way too low, currently at about 500rpm.
I have been messing around with the screw on the idle extra air valve but it doesn't solve my issue, because depending on the direction I turn it, the idle speeds either gets even higher or even lower. But I suspect it to be part of the problem.

The high idle even seems to affect the gearbox somehow, when coasting down from speeds > 50mph to about 1500rpm, it feels like it's having trouble shifting down and the rev counter goes up and down several times. I originally thought this was part of my gearbox issues but in the meantime I think it has nothing to do with it.
When the idle speed is too low, the alternator doesn't charge the battery and I am running into battery issues. So I definitely have to adress this issue.

Any ideas what to look for? Is the extra air valve a good starting point (I have heard that they can be cleaned but in hard cases a replacement part is more likely to solve the issue)?

Thanks!