Trouble when Starting - 1997 Buick Lesabre

[buick_boy]

I have a 1997 Buick Lesabre Custom. 145,000 Miles. I'm getting P0171(system lean) error codes in the past month. The problems happen when the car(Bert) [] : has been running at operating temperature, then sits for ~5 - 10 minutes and then I try to start it again. It will fire but sometimes die right away, most of the time it will continue to fire but it will barely idle. After I give it some gas it will finally cough it's way up to idle speed and then level out. After this, the car will idle but intermitently miss and hesitate at idle speed. When I press the accelerator it will hesitate and jerk around a bit. After about 5 minutes of driving it idles great, no problems. I have never had problems when I start it in the mornings and it's cool out (knock on wood)? I have replaced several items in the past month including : pre-catalytic O2 sensor, Spark Plugs, Spark Plug Wires, PCV valve, Air filter, Fuel Filter. I cleaned some major grounds, don't think I got all of them though. I'm at a loss for what could be causing this? Any thoughts?? Please?

[Flatrater]

Well a code P0172 lean system would mean either you have too much air entering the engine or not enough fuel. I would take a real good look at the vaccum lines. Make sure none are loose or off!

[buick_boy]

I broke down and took the car to the shop, first one checked my fuel pressure and said it was fine. The dealership then checked it and they said it was horrible. 25 psi at time of crank and should be ~ 43 - 45. Replaced the fuel pump and the car runs great.