EGR block off plate?

There is no good reason to delete the EGR on a street car.

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

Well to be honest with you i wouldn't just take what Jrichker said and run with it. Do some research!!! Make an educated decision. Jrichker is a smart guy and everything he told you is correct. BUT...with a custom tune...the EGR is not needed, and honestly its ugly.

With a custom tune you can shut off that entire function/logic in the computer. This means that every fuel and timing function/table that incorporates the EGR will not work. The car will just run on the fuel and timing tables that do not incorporate an EGR multiplier or adder.

The mileage gains you will see with the EGR remaining functional are really insignificant. I have been running with a properly deleted EGR (Tweecer) for a year now...and i still pull down 23+mpg in the winter and 25+mpg in the summer (different tunes).

Do you research and make the decision for yourself. This way you have the satisfaction of knowing a little more about your car and tuning it. You may decide the EGR should stay..thats fine. But if you do want to delete it...i made my own delete plate for $1.67 and some band saw and grinder time!

Check out www.eectuning.org and search for egr...that will tell you all you need to know about tuning and the EGR functions/logic in the computer. good luck man.