p0171 code

[tangel]

i have a 99 ranger 2wd 5 speed. i keep getting p0171 cel. i had low fuel pressure, 46 psi, and i thought this was the culprit. not so.

i replaced the fuel filter, fuel pump, all vacuum lines, cleaned the maf, and still i get this code.

my fuel pressure is at 66 psi, well within specs. i am at a loss unless the maf is bad.

does anyone have any ideas or things i've missed?

 

[pillen140]

thats not bad fuel pressure, its running lean, which means more air than fuel in the mix. could just be an o2 sensor, could be just your maf [try junk yard(pocket item )] could be more serious problem, but id try those first. also check for intake leaks by spraying carb cleaner around the intake manifold and see if it causes it to shudder.

 

[modelageek]

did you follow the directions precisely on the CRC maf cleaner can

my thoughts

-maf/ check air intake box and airfilter for correct fit

-vacuum leak

-dpfe sensor/ clean EGR valve and check hoses and tube

-a p0171 is usually NEVER the o2 sensor

http://www.aa1car.com/library/ford_lean_codes.htm

 

[tangel]

i read the can and did exactly as it said when i cleaned the maf. no change.

i took a propane can and ran it all around the hoses and intake no change in idle. i changed both parts of the intake manifold gasket. and every vacuum line.

i have replaced the egr tube, but not the dprf sensor. i replaced both of the vacuum lines on the dprf sensor.

i should note, aftr i changed the fuel filter and fuel pump the cel light went our for a while but then came back.

i also am only getting about 21 or 22 mpg. its a 5 speed and 95% of my driving is freeway driving. i'm going nuts here trying to figure this thing out.

 

[modelageek]

i read the can and did exactly as it said when i cleaned the maf. no change.

i took a propane can and ran it all around the hoses and intake no change in idle. i changed both parts of the intake manifold gasket. and every vacuum line.

i have replaced the egr tube, but not the dprf sensor. i replaced both of the vacuum lines on the dprf sensor.

i should note, aftr i changed the fuel filter and fuel pump the cel light went our for a while but then came back.

i also am only getting about 21 or 22 mpg. its a 5 speed and 95% of my driving is freeway driving. i'm going nuts here trying to figure this thing out.

did you add some Techron to the tank in case you have a sticky/clogged injector?

did you replace the entire fuel pump assembly or just the pump...........for you fuel pressure test how many cycles of the key did it take to get to full pressure for the koeo test? what was the koer?, how long did the system hold pressure after you turned it off. The DPFE sensor are a common failure but most of the time they throw the p1401 code

 

[tangel]

i ran fuel injector cleaner throug it right after the filter and pump change.

i replace the pump only, not the assembly.

i get no pressure with just the key on, with the engine running it held a steady 66psi, the minute i turn it off the pressure drops to nothing.

i figured it was a faulty relay but i understood the relay's primary function is to make easier starting.

 

[modelageek]

i ran fuel injector cleaner throug it right after the filter and pump change.

i replace the pump only, not the assembly.

i get no pressure with just the key on, with the engine running it held a steady 66psi, the minute i turn it off the pressure drops to nothing.

i figured it was a faulty relay but i understood the relay's primary function is to make easier starting.

you should have about 65 koeo. it should get to that pressure within 2 or 3 cycles of the key. you also should drop no more than about 8 psi in 5 minutes after turning the truck off.......The check valve and the regulator are part of the assembly......Techron is the Best.......did you use a lot of shell gas by any chance..........if you have a way of checking for power at the pump koeo I would do that.....if you have power there when the key is first tuned then I think you have something wrong with the fuel pump assembly.........when the pressure drops immediately after turning the truck off that usually indicates a bad/sticking check valve......

 

[modelageek]

also if that was my truck.......I own a stethoscope and a cheap code reader........I would check that each injector is clicking and I also would occasionally check for codes........a lot of times you can catch a pending code.....a pending code does not set the CEL off..........the issue has to happens a bunch of times for the cell to go off...........I catch a lot of issues this way.....I doubt it is the injectors because I think the truck would be running worse and throwing more codes but it is good to eliminate stuff...

 

[pillen140]

Did you ever figure out what was wrong with it?

 

[tajvelocity]

I had this code forever as well. I sprayed carb cleaner on some vacuum hoses and heard the idle go up. I replaced that hose (not sure what it's called) and unplugged the battery to reset it and it hasn't come back on. My light might be out though. Anyway, it runs a lot better. It sounds like you already tried that trick though.

 

[tangel]

I have not fixd it yet. i was thinking about changing the fuel rail pulse dampner, i'm thinking this is why it isnt holdin gpressure after shutoff or with koeo.

i also didnt realize there was a fuel pressure regulator in the fuel pump assembly. i dont really fell like pulling ht epump out again but i may have to.

 

[modelageek]

I have not fixd it yet. i was thinking about changing the fuel rail pulse dampner, i'm thinking this is why it isnt holdin gpressure after shutoff or with koeo.

i also didnt realize there was a fuel pressure regulator in the fuel pump assembly. i dont really fell like pulling ht epump out again but i may have to.

I guess you don't believe the info we are giving you and that is fine. it is your choice to do that...........that being said it is not your fuel damper........it is most likely the check valve..did you add a large bottle of TECHRON to the tank?

* I just reread the thread......it is a pretty tough thread to follow..on one of your last posts you said you got no pressure KOEO.....if this is true then you have a different issue.

 

[tangel]

i must not understand. i assumed the check valve was part ot the fuel dampner set up, and im assuming the fuel dampner is the same as the fuel pressure regulator.

yes i ran techron through the system, no change.

i have not pulled the bed off again to cehck the pump, but i can hear it kick on.

and yes with koeo i get no fuel pressure. also the minute the engine shuts down the pressure goes to zero.

 

[tangel]

well i ran another can of techtron cleaner through the system, i installed a 1 way check valve between the tank and the fuel filter, still have the same problem.