Modulator and vac hose are new to trans. In fact, all the rubber on the engine is new. Either way, its the restart that is odd since it fixes the issue. Trying to think what vacuum part could do that trick and all I think of is the idle valve. But if that was open wide I would think rough/high idle.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car