HI everybody -

I'm battling the infamous P0171 at the moment. Starts great, slight stumble under accel (getting back on gas after shifts) and slight hesitation at part/light throttle cruise.

Things I've replaced

Intake hoses
Intake manifold gasket (upper only)
Vacuum hoses
Upstream o2 sensor
EGR valve
Fuel Filter

I'll be taking this in for a smoke test to confirm/deny any vacuum leak sources. I also have yet to check my MAF

In the mean time I did check my fuel pressure today. No pressure reading with just ignition on.
Motor cranks, starts - fuel pressure slowly reaches 30psi.
Disconnect FPR, pressure rises ( good FPR)
Fuel pressure responds positively to throttle blips

Isn't the fuel pressure supposed to rise almost immediately? I can smell fuel vapors from the rear of the truck, will investigate - not sure if the culprit would impact drivability (there's no vacuum lines back there that I know of...?)

Would appreciate your input!

Thanks everyone,

 

Hey, I've got the same problem. Take a look at this guy's vid he's got the same symptoms as yours and my truck.

 

Simple vacuum leak test is to warm up the engine then let it idle, 2.3l should idle at 800 with automatic, 700 with manual.

Now unplug the IAC valve it will close and idle will drop to about 500rpms, or engine may even stall, either is good and means no vacuum leak.
If idle stays high start pulling off vacuum hose from intake, one at a time, and plug intake port with your finger, if idle drops that hose has the leak, follow it.

'97 Ranger fuel pressure should be 35-42psi

Yes, you should have at least 30psi when engine and key are off, system should hold pressure for a few months, not minutes.

Fuel pump will run for 2 seconds each time the key is turn on, so cycle the key on then off then on again to get fuel pressure up and then turn key off and see if it holds pressure.

If not then either fuel pressure regulator is leaking, or the check valve in the fuel pump is bad.
Because you only get up to 30psi I would suspect the fuel pump, and since you smell gas in the rear of truck I would suspect a cracked hose fitting on the top of the tank.

 

Ok man, new fuel pump installed on Tuesday, cleared codes, ran for the last three days. Truck idles much better/accelerates much better, no more error *knock wood*. so I changed the fuel pump and the pressure regulator.