Nissan Repair Questions? Ask a Mechanic for Answers ASAP
Can you remove the spark plugs, and crank the engine to see if excess fuel comes out one cylinder?
Fuel pressure of 9psi points to an injector stuck open.
You have just changed the spark plugs, haven't you?
Just remove them, leave them out, leave coils disconnected, 2nd person crank engine, and view what comes out of which cylinder.
Have seen many injectors stick open, and partly flood engine, misfire while running, and also hydraulic engine, bend rods etc.
Ok, I'll wait for you.
I wish you some luck for some answers/more info.
I hope my advice has been of assistance to you.