A simple way to test egr open or closed at idle:
disconnect vacume line between egr controlling solenoid and egr
valve(assuming your ride is so equiped) , then run the engine.
If idle has smoothed out, the controlling solenoid would appear faulty.You
could prove this out by sticking vacume gage on the downstream side of the
solenoid.Should be no vacume. Then, with engine still running, connect a
vacume source directly to egr valve, if idle becomes lumpy with vacume
applied and smooths out when released, it would prove egr valve is
Further, I have proven that the egr is controlled open under most part
throttle settings and will close at WOT by connecting (tee in) vac gage
between control solenoid and egr valve. If I'm not mistaken, at WOT, ecu
control goes open loop therefore closing egr.
If you leave the vac line between the solenoid off , go for a drive, chances
are the ecu will set the egr code because map sensor has not sent the
correct value signal back to the ecu.
Ecu is looking for set values based on CTS, TPS, MAP, Knock and VSS(again
assuming all sensors are working properly).
Doc feel free to correct me...