My 98 Mazda 626 2L ATX has a fully electronic EGR valve controlled by the ECU. I've been trying to figure out a rough idle problem for a long time, which gets worse when the engine is under load, such as if the brake is held down in drive, if the A/C is turned on, or even if the radiator fan comes on, all of which cause more of a drop in RPMs than I would expect.
On a hunch I decided to check the EGR, and the ForScan software is showing that two of the four EGR control motors are "ON" basically all the time, even right after starting up the engine before it's even warmed up. I don't know if the ECU is reporting what it's commanding, or what it's detecting.
I'd checked the resistances on the pins with the engine off a long time ago and they were all in spec at about 22 Ohms, so I had ruled the EGR out based on that. However, now I'm having second thoughts.
So, is it normal for the EGR to be active at idle? If not is it possible that the ECU is turning it on due to some other problem, or that the ECU is simply showing it on because it's stuck open? If it's stuck open wouldn't that cause some kind of DTC?
I pulled the EGR off and cleaned it. It seems to be seating fine. It's the type which is a single plunger held closed by a spring. The only thing the ECU can do is open it. There's a picture of it here. Cleaning it didn't have any effect on my idle quality. I also tried unplugging it, which also had no effect.