II can help you in a very simple manner. Ditch the color coded lines. They are useless if you are not going to an auto
show where everything must be in factory new condition.
EGR plumbing: One line from any of the vacuum ports on the intake manifold to the bottom vacuum port of the EVR
(electronic vacuum regulator) mounted on the rear of the passenger side strut tower. One line from the top vacuum
port on the EVR to the EGR (exhaust gas recirculation) control valve mounted on the throttle body spacer.
Just in case here’s a tech note on the EGR system.
Some basic theory to clarify how things work is in order…
The EGR shuts off at Wide Open Throttle (WOT), so it has minimal effect on performance. The addition of exhaust gas
drops combustion temperature, increases gas mileage and reduces the tendency of the engine to ping. It can also reduce
HC emissions by reducing fuel consumption. The primary result of EGR usage is a reduction in NOx emissions.
The EGR system has a vacuum source (line from the intake manifold) that goes to the EVR, computer operated electronic
vacuum regulator. The EVR is located on the back of the passenger side shock strut tower. The computer uses RPM, Load
and some other factors to tell the EVR to pass vacuum to open the EGR valve. The EGR valve and the passages in the heads
and intake manifold route exhaust gas to the EGR spacer (throttle body spacer). The EGR sensor tells the computer how far
the EGR valve is open. Then computer adjusts the signal sent to the EVR to hold, increase or decrease the vacuum.
The computer adds spark advance to compensate for the recirculated gases and the slower rate they burn at.
Troubleshooting:
There should be no vacuum at the EGR valve when at idle. If there is, the EVR (electronic vacuum regulator) mounted
on the backside of the passenger side wheelwell is suspect. Check the vacuum line plumbing to make sure the previous
owner didn’t cross the vacuum lines.
Diagram courtesy of Tmoss & Stang&2birds. (the diagram says 88 GT, but the EGR part is the same for 86-93 Mustangs)
The EGR sensor is basically a variable resistor, like the volume control on a radio. One end is 5 volt VREF power from the
computer (red/orange wire). One end is computer signal ground (black/white), and the middle wire (brown/lt green) is
the signal output from the EGR sensor. It is designed to always have some small voltage output from it anytime the
ignition switch is the Run position. That way the computer knows the sensor & the wiring is OK. No voltage on
computer pin 27 (brown/lt green wire) and the computer thinks the sensor is bad or the wire is broken and sets code 31.
The voltage output can range from approximately .6-.85 volt.
EGR test procedure courtesy of cjones
to check the EGR valve:
bring the engine to normal temp.
connect a vacuum pump to the EGR Valve
apply 5in vacuum to the valve.
if engine stumbled or died then EGR Valve and passage(there is a passageway through the heads and intake) are good.
if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is blocked.
if engine stumbled, connect vacuum gauge to the hose coming off of the EGR Valve
snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
did the vacuum gauge show about 2-5 in vacuum?
if not, check for manifold vacuum at the EGR vacuum valve.
if you have manifold vacuum then connect vacuum gauge to the EGR valve side of the vacuum valve and snap throttle
to 2500 RPM.
should read about 2-5 in vacuum
Late Model Restoration has the Ford Racing M-12071-N302 kit with the EGR valve & sensor along with the ACT & ECT
sensors for $45. See
http://www.latemodelrestoration.com/iwwida.pvx?;item?item_no=M12071N302 1&comp=LRS
for more details
