Hi all, Hope you can help with a problem I've been fighting for a while. I get a random rough idle and stall in my 97 Z34. Thought it was an issue with the spark and proceeded to replace coils, plugs, etc.... Replaced fuel filter about 3 months ago. I get 30 psi fuel pressure reading with ignition on. Drops to low 20's at start and stays at 30 psi during idle. Drops down to 22 psi under high revs. Manual says I should be around 40-31 psi at idle and 40ish at ignition. What would cause low fuel pressure? I though fuel pumps are all or nothing. is there anything else that could cause low fuel pressure? Sure do not want to drop the tank and install a new pump.

 

my guess would be fuel pressure regulator (cheap fix worth trying) or the fuel pump itself....