2002 S10 SES code P0171

[Lowrida18]

So I had my buddy put his ODB2 scanner on it and found its running lean so its starting horribly. I got a 2.2l vortec. So i changed my fuel pump as I took it in to get the fuel pressure tested and it was only at 31 psi and as soon as i shut it off the fuel would run right back to the tank so thinking maybe no fuel pressure. When its really hot outside it starts worse it shakes and is very hesitant also runs like crap till pressure builds up when driving. Ive been researching this code not only on here but also on google trying different troubleshooting but i dont know much when it comes to the electronics on these trucks. I changed a vacuum hose that was all warn going to the throttle body thinking that there may be a leak causing the problem but still doing the same thing, I also tried cleaning the MAP sensor but that didnt do the trick either. I really need help with this any ideas would be greatly appreciated. I also just changed my fuel filter just about 2 months ago so I know thats fine, I also tried running injector cleaner through it.

Thanks

[laydout97]

what about the fuel pressure regulator?

[Lowrida18]

thats one thing i was thinking to check next from what ive read not sure exactly where it is or what it looks like i read it is vacuum operated also and if the hose comes off this problem could happen. where exactly is the regulator located and what does it look like

[702s10]

it's near the firewall under the last intake runner

[Lowrida18]

i was just out working on it with no luck im still unable to find it ive looked at some pictures but nothing. I was just wondering where the throttle body connects on the driver side through the air flow theres a small hose going from the motor going up into that flow box and i pulled the box off to see underneath and in that hose theres gas or something in there is this normal? or may it be caused by a leaky fuel injector?

thanks

[weezin355]

Is this a flex fuel vehicle? If it is, then the fuel pressure regulator is part of the fuel filter. If it is not a flex fuel then as stated by (702s10 "near the firewall under the last intake runner") on the back of the fuel rail between injectors a fuel hose. I attached a pic, thanks to (wicked mayhem), which is a shot from front to back under the intake manifold runners, you can see the four injectors and the FPR in the back marked with red arrow.

[Lowrida18]

ok so i just found out last week that my truck is flex fuel i havent had a chance to come online. I did change my fuel filter maybe 2 months ago just picked up a regular filter not a flex fuel filter as i run regular fuel im wondering if that would make a difference but i was told otherwise. also could it be my map sensor im going to swap mine out with my buddy to see if that does anything i know theres a flex fuel sensor which is like $1200 but i had a mechanic look at it and he doesnt think thats the case but im not sure i didnt even realize it was a flex fuel system.