94 tercel missing on cyl #2

Help!! my friend has a 94 tercel that shakes real bad at idle. He asked me if I could check it for him and I said sure. What I found was that there is a misfire on cyl #2. I took off the spark plug cable and checked for spark, which there was. So Itook off the plug and it was cover with carbon. I kinda hit it with a socket and all the carbon fell off. Then I disconnected the injector and had no effect on the engine's idle. I also disconnected cyl #1 injector and the engine died. So my best bet is that the injector could be bad. It was changed not long ago with one from the junk yard. I also saw that there was some gas leaking form the top O-ring. What is your suggestion?