What are the signs of a bad EGR valve?

 

Fluxuating idle and mis-fire at steady speed w/slight throttle pressure. There are a few things you could do to test it. 1) unplug the vacuum line and put a golf T in it to plug it, then drive the car to see if the problem stops. 2) test the EGR vavle w/a vacuum pump and gauge to see if it'd hold vacuum. 3) unplug vacuum line, reach under valve and manually depress(you'd press upward, toward the sky) the diaphram then place your finger over the vacuum port on the valve and let go of the diaphram. If it doesn't hold vacuum it's got a vacuum leak. 4) buy a new EGR and see what happens. If it's the original EGR valve, then i'm willing to bet that's the cause.