symptoms of no EGR??

I dont know if its erg specific...sounds like a vac leak to me. What merc are you pulling?

Refers to mercury...measured in hg. If you hook up a vacuum gauge to your vac tree you should be pulling 16-22hg (merc) on the meter. That can vary depending on what heads and cam your running. 16-22 is stock vacuum.

The EGR sources controlled vacuum from the EGR vac solenoid. The solenoid actuates with data from the computer (the solenoid only sends vac during cruise conditions).

If EGR was active at idle (it should not be), the car would want to die, not surge and take off (I agree that this symptom sounds like a vac leak or bad TPS, IAC, etc).

If your EGR was not working at all, the car might ping at part throttle/cruise (when EGR should be working).

If you want more info on the EGR (I doubt this is your issue), I wont even try. I would read Jrichker's awesome posts about it. You will know more than you ever wanted to.

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 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 EGR valve and the passages in the heads and intake manifold route exhaust gas to the EGR spacer (throttle body spacer). The computer uses RPM, Load. and some other factors to tell the EVR to pass vacuum to open the EGR valve. 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.

Diagram courtesy of Tmoss & Stang&2birds.


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 5in 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 5in vacuum

Skoobie said:

Refers to mercury...measured in hg. If you hook up a vacuum gauge to your vac tree you should be pulling 16-22hg (merc) on the meter. That can vary depending on what heads and cam your running. 16-22 is stock vacuum.

Click to expand...

Mercury is actually measured in millimeters, hence mm of hg.

*edit* Hold please while I go slap myself for being anal like that.

mrswivlepants said:

Mercury is actually measured in millimeters, hence mm of hg.

*edit* Hold please while I go slap myself for being anal like that.

Click to expand...

Are we real sure about that?