P0171 & p0174 I searched

[Madmark]

I have a 1998 ford ranger 4.0 efi and I am getting p0171 and p0174 codes. I have sprayed the engine for vaccuum leaks and found the upper intake manifold gasket leaking. Replaced that and it ran better but still idles ruff at idle and setting the codes still, replaced fuel filter and fuel pressure is 30 psi at idle, still in range right? O2 sensors are working fine

I have Tryed every vaccuum line I can find and doesn't get better, replaced pcv as well... If I disconnect the maf the engine runs fine and no longer runs like crap. Another thing is in the mornings it is hard to start so leads me to think fuel pump

Any help I would appreciate it, I'm confused if I should try a new maf or new fuel pump

 

[RonD]

I would clean the MAF
http://www.therangerstation.com/tech_library/CleanMAF.html


In the morning try turning the key on then off a few times before cranking the engine, so prime the fuel system by starting the fuel pump a few times.
If this gives you a quick start then you have a pressure leak somewhere.
And it could be in the fuel pump assembly.

 

[Madmark]

Forgot to mention that I have cleaned the maf and when I run the key over ( testing prime pressure) it is 10psi

 

[RonD]

Your fuel rail also has a regulator/return line, I think the 1999 and up didn't have this.
The regulator has a vacuum line, remove the vacuum line and check it for fuel, a leaking regulator diaphragm can cause the lower pressure.

But it is looking like a fuel pump/check valve issue
Pressure should be above 35psi at idle and above 40psi at 2k RPM

 

[Madmark]

I pulled the line off the regulated and no luck, ran just as ruff if not more and no fuel was leaking out

 

[Marcdam9]

I have a 99 ford ranger 4.0, 2wd, auto trans & according to some research I did, found out that the fuel pressure regulator is located in the tank and must be bought as an assembly if it is not maintaining correct fuel pressure. Furthermore, found a vid on youtube about a pressure test on a similar model. I actually have the same codes as well about a vacuum leak & running lean bank 1. Don't have my codes since i lost em & need to get it re-diagnosed. Trying to figure it out. idles crappy & hesitation.