Cold start valve = cold start injector, I assume, and it's part of a system also including the idle control valve and the temperature sensor.

These three provide the equivalent of "choke," meaning a rich mixture accompanied by a little extra air. The system does nothing unless the temp sensor tells the computer the engine is cold, of course.

Vacuum leaks, obviously, rather defeat the goal of providing a rich mixture, but you appear to have addressed that possibility. Even the o-ring on your engine dipstick is a vacuum leak possibility.

You can search the forum for "idle control valve" to learn procedures for testing, cleaning, and/or replacing this item. When a cold engine is trying to idle with a rich mixture you need this component to provide a bit of extra throttle--your low rpms suggest it may not be functioning.

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles