I have a 1995 Chevy S-10 Blazer. I had the check engine light come on, and the codes said that it was the oxygen sensors. I replaced both sensors, and everything was fine for about a week and the light came on again. I took it back to run the codes again and it was th O2 sensors again. I was told that there could be another problem, that would cause them to fail in such a short time. I also noticed that when I am at a stoplight, it idles rough. I was told that the fuel is running rich. What other things should I look for in order to fix this problem?