1999 Nissan Frontier Will not run, misfire.

Just bought the truck, so no history. Symptoms: hard start, will not stay running, misfire, backfire, black smoke out tailpipe, spit, sputter, b##ch and complain then die, generally runs like crap when it does run. Pulled code for crank/cam sensor, replaced, code gone. Cleaned MAF, no difference. Checked for vacuum leaks, none visible. No more codes, but emissions warning lights on scanner are lit up like a Christmas tree. Any common problems with Frontiers or a place to start would be appreciated.