EGR

that sounds identical to when my egr went bad. apply vacuum to the egr (i just used a hose and sucked air through it), and see if it holds vacuum when you do this. mine didn't. i tried cleaning it ant the pintle valve but it didn't help.so i i think my diaphragm had a leak somewhere. i replaced the whole egr and problems went away. have you ran the codes yet? egr is 33 i believe?

when you say you got no vacuum what do you mean? you will have no vacuum coming from line going to the egr at idle. ther is no vacuum going to the egr at idle or wot only part throttle.If you have a vacuum gauge and pump you can test the egr and you can put a T in and then snap the throttle to get a vacuum reading. A common issue after talking with parts guy at ford/and bloopbloob is the egr vacuum soleniod going south, they get crap in them. the part # is E 53 E 9J459 A1A the 9J459 # is the one they use and they had 6 in stock.I would also pull the egr off and do what bloop posted suck on the fitting and see if the diaghram pulls back and holds vacuum of it does the egr is good, then clean the egr and get out as much carbon has you can.

I had the same issue and changed the egr vacuum sensor and egr positioning sensor which bolts onto the end of the egr, and cleaned it and now I'm fine, I stalled at lights and when slowing down like you put in the clutch and rpms fell. also when you are done unhook the negative battery cable for about 30min to clear the computer. good luck.

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