Yes, could be an injector problem. I take it you do not have any problems starting it? Could be a timing issue, or dirt clogging the screen (If there is one right before the injector). I have an old muti-fuel diesel engine giving me the same problem. Check all the lines and make sure there they are tight and there are no pin holes or hairline cracks, allowing air to get in. It doesn't take much...
Hawk