The 3/2 valve is definitely crucial on my 300td to shifting. I have a weird symptom. I get completely intermittent vacuum. i can get the car to shift perfectly, but only by 'kicking' the throttle a few times-usually in neutral. I thought this was a faulty vacuum control valve, it's spring or internal diaphragm somehow not returning to closed throttle/full vacuum. However, i put a brand new valve on and still problems. If i slightly open or close the 3/2 valve, the vacuum comes back up temporarily. However, with good vacuum at closed valve, when the throttle is applied fully, sometimes the vacuum just drops to zero and won't come back up.

I think the 3/2 valve must be leaking somehow. When the throttle is closed, the valve is completely closed as well, which is what a mercedes mechanic told me is correct--ie, the cam on the 3/2 valve pin should be completely at rest, leaving the valve closed.

Please help!! BTW, it's a brand new valve.

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Mike
Vancouver, BC
'79 300td 60k miles!
import from Japan