Nissan Repair: rough idle/timing mark, fuel pressure gauge, haynes manual

Question
I have a 1990 maxima that runs rough. I CHECKED THE TIMING WITH A LIGHT and see that it won't stay at the 15 btdc mark,I've turned the distributor to no avail. I made sure it was on the #1 spark plug and etc.. Could the fuel injectors be bad? How do you check for bad injectors?  

Answer
Kevin,

There is a sticker on the hood that shows what to disconnect to get the base timing set.  The problem you are having is the computer keeps moving the timing on you while you are setting it.  If it were me I would put the distributor back where it was before you started and then start from there.  Get a fuel pressure gauge to check the fuel pressure.  Screw it in the injector rail and start the cart.  Get a Haynes Manual to get the specific pressure for your vehicle.  Now, turn the engine off and if the pressure drops to zero really fast, like immediately, pull the plugs and check for those that are really black and you will find the injector(s) that are defective and leaking.