What should the proper Fuel pressure specs be? I put a gauge on my car today and at first prime the pressure spikes to 49-50 then when the pump turns off the pressure drops to like 10 or less and slowly drops. when you start the engine it pops up to 48-49 or so and stays there until you pop the throttle and it dips 5 or so then returns. If i hold the throttle for a bit it drops and hangs there. when you turn off the car it Instantly drops to 10 and then slowly drops to 0 again.

I have no vacuum leaks, no exhaust leaks, i have no SES codes, it runs perfectly smooth But it just wont go like it used to. on the highway i used to be able to maintain 65 with only light pedal but now im using like half and it kicks down on some of the steeper hills when in cruse which it NEVER used to do unless i was at WOT. I cant figure this out i cant find ANYTHING wrong other than this funky fuel pressure. I have checked my spark plugs and they all look normal. also in town i am using a lot more pedal than i used to.

 

For your key on Prime check.

When you first turn the key on, the prime pressure should be around what you observed. Mine is around 50 at prime. It will lose pressure as soon as teh pump turns off, but shouldn't dip below 40. However, with the car off, it holds pressure for 10 minutes at over 30 psi.

Running

The fuel pump should stay around 42psi at idle. When you hit WOT, the fuel pressure regulator should pump the PSI up to 48. There will be a slight dip first, but nothing more than a blip.

-Sounds like something is wrong. If your FPR isn't holding pressure on prime, it will bleed pressure back to the tank. If you have a leaky injector you will see the same. I would recommend getting a rebuild kit for your FPR ($14) and see where you sit.