I have a 1997 GMC Sierra. The truck runs fine except when I am stopped at a light or in traffic. The engine idle is rough...but it never dies. The SES light comes on often and I have replaced fuel filter, air filter, plugs, wires and one O2 sensor but the problem is still there. Could this be a problem with the Idle Air Control valve?

Could also be the EGR valve. If you're truck is throwing codes, then take it in to autozone, they will print out the codes for you and give you a piece of reciept paper with the codes and explainations on them. also, if it is the EGR vavle, you can take it off, clean it with some carb cleaner and put it back on. I had the same problem in my 96 sierra and it fixed it. also, another thing to try is to just let the truck sit a couple days, walk out, and try to start it. sometimes its just the computer being moody, especially on vechicles this old, now im not saying thats a permanent fix, but it should get you going long enough to find out what your problem/s is/are

Yes the idle air control valve or map cencer