1999 buick lesabre 3.8 with 208,00 miles, the car starts hard and then idles very rough, i have to pump the accelerator for 30 seconds so it wont stall had a code of P0171, I did find the 90 degree elbow connector to the fuel pressure regulator had a big crack along the side, replaced that and that helped for awhile , I disconected the battery for 30 minutes and then reconnected the battery to clear the codes, drove it around for awhile but it returned the code came back and the same hard start and rough idle had a new fuel filter replaced and it has gotten worse

an added note, after letting the car sit over night, I started the car this morning and it started up normal and idled normal, drove around for 30 minutes and parked in the garage and went inside the house, came back to the garage after 10 minutes started the car and got a hard start and rough idle again

also check engine light came on P0171 code

Have you tried anything to diagnose your lean code?

no, other than search the code itself that it gives a list of possible problems like MAF sensor, fuel pump, fuel regulator etc

I am at a loss on what to do next

I did install a new MAF sensor that was manufactured for the duralast brand from autozone, dont know if this is good product or not??????

I had a check engine light, went to Oreillys to use the scan tool, got a P0171, came back home with some carb cleaner and while the car was running I sprayed different areas around the intake manifold and any vaccum hoses to see if they was any kind of change, no results there, i got into the car to drive it around and the check engine light was off

It sounds like an intermittent vacuum leak.

How long have you owned this car?

How many miles have you owned this car?

Has the upper intake manifold been replaced?

Has any other work been done to the engine within the last 1,000 miles?

i have had the upper intake manifold replaced 5 years ago, it currently has 208,600 miles on the car itself, yesterday I had the fuel filter replaced, new mas air flow sensor 2 days ago, i am going to get a new fuel pressure regulator and put that on, the check engine code went away when i sprayed the vaccum hoses and the upper intake, it acts like it is starved for fuel when i start the car and there is a loss of power when driving down the road, especially when i when i step on the accelerator to pass a car, it will sputter some and some backfire, then it seems to catch up and have power