Nissan Repair: Fuel smell, rich mixture, fuel pressure gauge, fuel pressure regulator

Question
!988 Pathfinder:  3L  Recent work, O2 sensor, tune up, new wires cap rotor plugs fresh filters.  Runs great, starts up, gets poor mileage. I can't pass emission test.
Hydrocarbons and co 3X above passing. After driving fuel odor, stinky exhaust. So, I have a super rich mix, what are the next steps to correct?

Answer
Robert,

Either the fuel pressure regulator is blown causing way too much fuel in the system or you have a leaky injector or two.  Get a fuel pressure gauge and check the fuel pressure at idle.  Then, check the fuel pressure when the engine is turned off.  If the pressure falls fast that means you have leaky injectors.  These are the two most common problems from what you describe.  Pull the sparkplugs and note which hole they come out of.  The ones that are black and wet are those with leaky injectors.  That is, if the fuel pressure regulator checks out.  Get a Haynes Manual for your vehicle for the specific fuel pressure that it is supposed to read.  The book is $20 bucks and a fuel pressure gauge is about $35 bucks or you can rent one.