Hi, im troubleshooting the vacuum system in my 1984 DT. Here is what ive found so far.

1, the vacuum is fine when taken at the brake hose.
2, The vacuum is fine when taken anywhere else.
3, the only time the vacuum disappear is when (any) throttle is applied.
4, I plugged the hose going to the lower of the 3/2 valves(on the valve cover) and then the vacuum decreased proportionally with throttle application. I took the car for a drive in this configuration and the shifts seemed to be smoother (although 1-2 shifts were still hard)
5, there is no vacuum going from the white line originating at the 3/2 valve to the vacuum control valve.

What does the lower 3/2 valve do?

Get rid of all the lines to and from the black box. There are two lines that run from the driver's side from T's. Remove them and also remove the T. Then connect the two remaining lines that previously went to the T with a short piece of hose.

The third line goes to the temperature switch in the thermostat housing. Get rid of this line as well.

what would the consequeses be of bypassing that 3/2 valve? what does it do?

thanks

It controls the function of the EGR valve. There are no consequences.

I apologize for my spelling, i admit its horrible...