Echoing JIm on the old back-stabbed receptacles; if you're having circuit problems, just go ahead and remove all of these. In my limited amateur wanderings, I've seen at least half a dozen of them with wires hanging completely loose, and others that failed completely but still looked okay. The new back-wire receptacles that tighten with the terminal screw are great, and would be a very easy replacement. Even if the old ones are working now, they're a high risk to fail in the future.
Originally Posted by jadnashua
And along the way, like Rick said, look for wire nuts with multiple wires; easy for somebody to goof on. I have in the past...:o