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Check Engine Light: P0171 & P0174


rabbit91

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2000 V8 lifted 33s
Bump have same codes after a rough start, curious to here of any successful remedies, going to double check all hoses and clean MAF. I'm surprised no one has mentioned changing the fuel filter... Or maybe I'm crazy
 

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KayDee

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Chico, California's...
Year, Model & Trim Level
2002 Ford Raner4×4
Bam..A hole in the hose

i had that problem, same codes + low milage and it turned out to be a vacuum tube with a hole in it right next to the throttle body.
There is a u shaped hose that rubs and there is a hole in it!
 


fritz24

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Powertrain DTC-Service information
P0171 system too lean bank1
possible causes:
1.Fuel System-
ethanol content in the fuel
Damage or leaking fuel pulse damper
Fuel filter plugged or dirty
Damage or worn fuel pump
Leaking fuel pump check valve
Leaking or faulty fuel injectors
Fuel pressure low, fuel supply line restricted, fuel rail pressure sensor bias
EVAP canister purge valve is leaking when canister is clean
2.Exhaust leak
3.EGR vac hose loose or disconnected
Valve tube/gasket/solenoid leak
4.intake air system
Air leaks after maf sensor
Vacuum leak
Pcv system is leaking or stuck open
Incorrectly seated engine oil dipstick
Intake air turbulence due to incorrect air filter
Faulty MAF sensor
5.secondary air injection
Damaged secondary air injection system or a mechanically stuck valve
 


PickleLips

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Year, Model & Trim Level
1998 Ford Explorer EB
This is the same exact issue that I have going on right now on a '98 explorer sport OHV. But there is no vacuum leaks. The MAF has been replaced. The one thing I have noticed that no one brought up was mentioning anything about fuel trim. Which is funny because when I turn the key on and don't start it the fuel trim is at 100% on both banks. When I take the negative and positive off and touch them together to reset fuel trim, the moment I plug in the scanner and look at fuel trim before even starting the truck the fuel trim is still at 100%. When I start it up, about 1 minute will go by until it goes into closed loop. There is no activity from the O2 sensors. The trim on the O2 sensors read 100%. When you unplug all 3 of them, it doesn't set a code. There's battery voltage to the heater on all 3. There's even ground. But on one of the wires there isn't continuity, which is common on the other connectors.We tried wiggling the harness with no success. The funny part about this story is that when all 3 O2 sensors are unplugged, no MIL is set, not even a pending code.



I'm fresh out of ideas. Anyone wanna take a stab at this?

For anyone's future reference trying to solve this issue, if your scan tool gives you live data readings like this with 100% fuel trim and 0 o2 sensor voltage, it is an issue with your scanners programming, these are not the actual readings. Sometimes your freeze frame data will still show the correct values for those parameters, so that can at least be some helpful knowledge. I found this one out battling this issue which is still ongoing. I replaced a horribly clogged fuel filter the other day and my mpg shot up to 16 from the usual 11 around town so fingers crossed.
 


rabbit91

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2000 V8 lifted 33s
Since this was dug up from the grave recently.....did anyone have any issues with upper RPM running with the same codes ? I have a 99 Xploder 5.0L

I have the same issues, also had a code that I thought was for a gas cap. Put a new cap, code never left. Just put another new cap and cleared codes but when I checked the stored codes it was for the P0171/0174. Have 3 stuck spark plugs on pass side to deal with, and a 1/2 stuck fuel filter.

But I digress.....to the upper RPM issue....above 3500rpm the truck loses power and doesn't want to go any faster, but when you let off the gas and the RPMs go down you can feel the speed and power pick up.

I was HOPING it'd be O2's.....but I bet the cat is clogged. I'm at 150K miles as well.

Thanks for any assistance. I'm going to see what my genius mechanic buddy what he thinks....but that'll be later this week.

Bump bump exactly what is happening to me, hopefully you get notified and had some
Success to fix this that you can share.
 


PickleLips

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1998 Ford Explorer EB
Bump bump exactly what is happening to me, hopefully you get notified and had some
Success to fix this that you can share.
My issue was a dying fuel pump. These codes are thrown due to either inadequate fuel pressure or a vacuum leak. Do a smoke test and hook up a fuel pressure gauge to figure out which it is. No power at high rpm sounds like lack of fuel.
 


rabbit91

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2000 V8 lifted 33s
My issue was a dying fuel pump. These codes are thrown due to either inadequate fuel pressure or a vacuum leak. Do a smoke test and hook up a fuel pressure gauge to figure out which it is. No power at high rpm sounds like lack of fuel.
That's something I do want to change as preventative maintenance seeing as I'm pretty sure the pump is still factory. Currently on the lookout for a fuel pressure gauge
 


PickleLips

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1998 Ford Explorer EB
That's something I do want to change as preventative maintenance seeing as I'm pretty sure the pump is still factory. Currently on the lookout for a fuel pressure gauge
You can rent one from Autozone or Harbor Freight has a decent one for like 20 bucks.
 


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