This is on a 1990 Ford Escort GT. Vacuum input comes from a T fitting
in-line with the EGR valve vacuum line, which is controlled by the EGR
vacuum solenoid. As such, I am assuming it receives vacuum when the
EGR valve does.
As for the two other vacuum lines, one goes into the EGR tube that
runs between the exhaust pipe and the intake manifold. The other goes
into the exhaust pipe opposite the EGR tube connection.
My guess is that when the device receives vacuum, it opens up a the
1/4" line running from the exhaust pipe (acutally end of exhaust
header) to the EGR tube, possibly to help feed the exhaust gasses into
the intake manifold. Or maybe used to sense exhaust back-pressure?
The reason I ask is that the 1/4" metal tube that was connected to the
exhaust pipe broke off, causing an exhaust leak. I fixed the hole and
am no looking into tapping a new hole into the exhaust header to
reconnect the 1/4" metal line.
In the meantime, just wondering what may or may not be happening while
the 1/4" metal tube is feeding fresh air (rather than exhaust) or no
back-pressure into the device that connects the line to the EGR tube.
The car also just passed NJ state emissions inspection a few weeks
ago, but failed for the exhaust leak. Seems like whatever is affected
did not have an impact on emissions.