Nissan Repair: engine vibration, fuel pressure gauge, fuel pressure regulator

Question
Dear Von,I own a Nissan FB14 1997-98 model (Automatic) engine no begins with GA. the problem of late is that the engine tends to vibrate and the car stalls. the mechanic i go to changed the spark plugs. even this has not resolved the problem as the plugs get black. first it was only 01 plug now its 02. what do you think is the problem & is it safe to drive like this? thanks a lot

Answer
Maas,

The engine is getting too much fuel and that is fouling the plugs.  I would check the fuel pressure to see if the fuel pressure regulator is blown first along with the fuel filter.  Lastly, I would check for leaky injectors.  Put a fuel pressure gauge on the engine adn note the injector leakdown to see which ones are giving problems.  If you turn the engine on and then off the pressure should stay for a few minutes.  If the pressure leaks down quickly you have one or more leaky injectors.  Also, have the injectors ohm checked to make sure they are within specification.  Remember that this thing is ten years old and things like injectors tend to wear out.