Faith and Works in the ECFs
One popular way of reconciling justification by faith with judgment by works is to appeal to Augustine's double-justification scheme, whereby at conversion we are justified by faith then live subsequent spirit-empowered lives of holiness and are at the final judgment judged on our deeds.
My own interest lies in the pre-Nicene Fathers' theology, rather than Augustine's (which is very different on most issues). Offhand, I cannot think of any evidence in any of the pre-Nicene writers to suggest they held to Augustine's double-justification scheme. So how do the pre-Nicene writers reconcile faith and works? Unfortunately that's not a question that's very easy to answer.
Universally in pre-Nicene writers, a strong belief in a final and eternal judgment by works is attested to. It is stated multiple times in most surviving documents and never denied. It is listed time and again as one of the major and basic tenets of Christianity.
Mention of justification by faith however is quite erratic. It is generally not mentioned very often. The Shepherd of Hermas, the longest document of the Apostolic Fathers, is all about judgment by works and just doesn't mention faith. Justin Martyr time and again repeats there will be a final judgment according to our good or bad deeds, and then just occasionally uses the word "faith" where one has come to expect him to say "works". First Clement emphasizes the importance of good works and how a doctrine of final judgment by works is to be taught to Christian children.
The majority of writers of this period follow Justin Martyr's style: Most of the time a final judgment by works is heavily emphasized, but on random occasion this will be swapped with justification by faith without warning, as if there was no substantial difference between the two. This leads me to believe that by and large the ECFs saw them as in some way virtually equivalent or synonymous (the alternative thesis being that they just had no clue about how to reconcile faith and works so swapped arbitrarily between them in a cognitively dissonant way).
The theory that seems to me to make most sense out of what they say, is to see faithfulness as the underlying heart attitude which works flow from and that God judges our heart not our actions per se. Thus they can talk about the doing of good deeds, having the right heart, being a good person, and being faithful to God interchangeably as ways of speaking about the heart and character of a person which is what God judges.
Another line of evidence to follow is that there is to some degree a clear demarcation between those who only talk about works, and those who use "faith" regularly. Now if you are willing to hypothetically consider an opposition between Paul and James within the New Testament on the subject of faith vs works, you could potentially construe the second century writers as following one or the other of these traditions and thus see a serious rift dividing the Christian theology of the second century into two camps. (The division within the second century documents is even more severe than what is found within the NT.) But there is no documentary evidence that Christians in the second century ever got into any arguments with each other on faith vs works issues, no suggestion that any such lines were drawn within orthodoxy. Furthermore, the group of writers who do use 'faith' terminology also use works terminology regularly. But if we want to deny any massive rift within orthodoxy, we have to really conclude that the theology of the authors that didn't use the word faith is substantially identical to the theology of the authors that do. Therefore, we'd want to conclude: Whatever the authors using the word faith meant by it, their ideas and theology could be expressed in language that talked about works without substantial loss of meaning. In other words, we'd conclude that faith and works have some sort of pretty compatible and substantially similar meaning.
So, when I read scholarly word studies about how pistis ("faith") was actually used in ancient times and find them concluding that it generally meant things like loyal obedience and faithfulness, I'm inclined to think "case closed, problem solved: 'faith' when you translate it right means something pretty synonymous with works, and that's why the pre-Nicene Fathers are generally happy to swap between them or use one or the other."