Ok. That valve is evidently working as it should.

When pulsing, I took the hose off and I do get a pulsing vacuum, off/on. With power disconnected I get NO vacuum whatsoever.

The other suggested issues are a vacuum leak somewhere, mass air flow meter (new one put in 4 months ago), and throttle actuator (replaced 4 months ago with a salvage part, same #, from a 96 model. It was cleaned very well inside and wiring looked fine.

This started after head gasket r/r so I'm leaning vacuum leak somewhere before replacing those parts again. The large tubes to intake and intake gasket were also mentioned as possible culprits in the vacuum leak scenario.

Thanks for the help and expertise. If you have a suggestion on isolating the vacuum leak that would certainly be welcomed.

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1994 C280, dark green metallic
105k miles

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(sold to another forum member)

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