Hello everyone I am having a problem with rough idle when I start my car but after I drive it goes away I checked and cleaned the grounds I replaced the manifold gaskets lower and upper and uppper intake manifold checked for vacuum leaks and replaced connections and some bad lines and replaced pcv and new plugs and wires and a new battery and new battery cables I had dtc p0171but it hasn't came back on since all the work I did its only been a day and a half but I still have the problem like I said after I start to drive it acts like it don't wanna go then its fine and I replaced my injectors and checked fuel pressure and its fine and by the way the car is a 1998 oldsmobile lss non supercharged if anyone has any answers or thoughts your help will greatly apprecitated

What was your fuel pressure? Was there any gas in the vacuum line that goes to the FPR?

Possibly MAF is dirty or throttle position sensor.

The fuel pressure is at 50 on the gauge and I changed the fpr because I smelled gas in the vaccum line and as for the maf I cleaned it with the crc cleaner and it didn't get better and I unplugged it to check if it was bad and I thought it ran normal but when I drove it and hit the brakes the car would just cut off like all the power got taken from it is that normal when u drive with no maf

Remove the throttle body and clean it. Also check the idle air control. My guess it that'* the problem.

You mention P0171, were or are there any other codes that were read?

(Dan...I'm already thinking EGR tube)

Kind of thought that myself, but wanted to check the IAC. To check the EGR tube he needs to remove it and visually inspect it. And doing that risks damaging it.

I have done all that cleaned the tb when I did the intake his weekend checked thhe egr tube and it was fine I didn't have any other codes and it hasn't came up again but like I said its een gone for a day in a half so it might come back I cleaned the iac and even tried changing it for a spare one off a junk car and no change at all I tried to list everything I did its pretty much everything anyone said to try about p0171 I wanted to make sure nothing else could cause it so I'm really stumped

What about the maf should the car cut off when I use the brakes with the maf unplugged or could that tell me what'* wrong

With the MAF unplugged the car will stumble at first and then run fine. If you have no real change unplugged the MAF is not the problem. P0171 is the biggest pain in the world to find and fix. Most of the time it'* a vacuum leak. After seeing all you have done, I'm starting to think it'* a vacuum leak in the HVAC system. And talk about a pain to locate. You said you swapped out the FPR because you could smell gas in the vacuum line? Check it again to make sure your not having the same problem. Because a leaking FPR will cause the very problems you have.