Nissan Repair: 89 nissan pk up 2.4, fuel pressure gauge, haynes manual

Question
my 89 2.4 nissan pk up is running extremely rick and blowing black smoke, I pulled a spark plug and it was black this model has 8 plugs I beleive 4 or for exhaust unspent fuel? any ides It does look like it will need a full tune up and a t-b cleaning????? what might I be missing

Answer
David,

If your truck is blowing black smoke I would be looking at the injectors and the fuel pressure.  Perhaps an injector is stuck or the regulator is not working.  Get a fuel pressure gauge and a Haynes Manual and check the fuel pressure and check for injector leakdown.  The sparkplugs could contribute but the extra set are really for more power and would not cause the black smoke if the rear set did not work.