Hi Folks,

New to the Forum. My 2001 F-150 gave me the codes P0171 and P0174 on a friends code reader. I am having trouble finding out what that means.

Thanks,

Scott

 

Banks 1 and 2 lean. Start looking for vacuum leaks; I'd recommend you start at the PCV hose that runs from the passenger's side valve cover to the rear of the intake manifold, closely inspecting the rubber elbows throughout the hose.

 

HI!... I don't want to hyjack this thread but tonight while cruising the strip, my truck started bucking and shuddering. It felt just like when your running on 6 or 7 cylinders due to a bad cop or a mis firing plug. I limped the truck home and started pulling plugs. All the plugs were good but the gap was off a bit. I had them set at 0.45 and they were at 0.55. It's been about 6000KMS since they were installed. So I re-gapped them and checked all mu cops and reinstalled everything. Start up the truck and it runs like crap again, just like a mis fire. Now the stupid SES light finally decideds to come on and I scan the codes with my XCAL-2. I also pulled P0171 and P0174 codes. Running lean on bank 1 and band 2. The weird thing is, that my INNOVATE MOTORSPORTS WIDEBAND gauge is telling me the truck is running pig rich at 10.5:1 at idle. It's usually at 14.7:1 (STOICH). Now I went throught the list on the FORD service CD. Now I have a mechanical fuel pressure gauge on my truck. 32PSI at idle and 41PSI at WOT. This is constant and has not changed. So it's not a fuel delivery or fuel pressure problem up to the fuel rail. Fuel filter is new. No fuel leaks and FPR (AEROMOTIVE) works fine. Vapour recovery system checks out, no vacuum leaks, PCV works fine, no leaks after the MAF, oil dipstick is seated, EGR system checked out fine.

I did run some C-16 race fuel in the truck a few weeks ago. It's leaded. But it was only 5 gallons diluted into 20 gallond of SUNOCO 94. Tomorrow I'll pull the O2 sensors and check them, also pull and clean my 42LB fuel injectors. If those two thing don't work, I'm lost due to everything else has been checked and triple checked.

Any ideas??????

 

Hi Scoodini, welcome!! Hi Neal, check this out, maybe you haven't seen it yet -

http://www.fordscorpio.co.uk/fuelmonitor.htm

 

The "lean" codes do not mean the exhaust is lean, it means that the PCM has enrichened the mixture as much as allowed but the O2 sensors are still reporting lean. Note the difference? Check your long and short term fuel trims for confirmation.

This code combo almost always indicates a vacuum leak that is common to both banks.

Steve

 

HI!... Well it's not a vacuum leak since I checked the vacuum lines and intake area plus sprayed some starting fluid around and no RPM jump. Also my AUTOMETER vacuum gauge is still showing basically the same amount of vacuum at idle it always has. I'm leaning towards dirty fuel injectors or bad o2's from the c-16. Since the o2's are less than 2 months old.

 

Clean the MAF sensor with Tuner Cleaner from RadioShack(leaves no residue).
DO NOT use carb cleaner,Throttle body cleaner,or brake cleaner. Those leave a residue.
GENTLY clean the sensor.It's very fragile. That's my $.02.

 

neal,

You may benefit by consulting TSB 01-9-7

Also, if you've modified your intake, the factory calibrations may be off.

What is your Freeze Frame Data?

Steve

 

Steve is correct.

You have "unaccounted" for air 'after' the air meter.
Many people mis-understand the 172/174 codes.
With this condition the codes always come up in pairs because unaccounted for air affects both sides about equally unless there is an air in leak at one cylinder runner.
The meaning of the codes is that they tell you the fuel tables have been leaned as far as they can go in the PCMs effort to correct, in actuallaty, a rich condition, not a lean condition, that you have already confimed with you wide band.
Again, codes are reflecting the state of the PCM reaction from sensor inputs and not the engine it'self. In this case, they are oppisite.
It's there, just have to find it.

 

HI!... MAF has been cleaned with electrical contact cleaner like always. Not the issue.

 

HI!... Intake manifold and intake have been modified for 7 years, no issues there.

 

HI!... Well I took every vacuum line off the truck and carefully inspected them. They are all in perfect condition and don't leak. Re-installed them and no change. Then took ethier and sprayed around all the intake and intake manifold gasket areas, just incase I have a gasket blowout which I highly doubt since the heavy plastic construction of FORD's stock gaskets.

Could it be two bad o2 sensors? That's the ONLY thing from the FORD service manual that has not been triple checked.

 

I would guess that the leaded gas, even though diluted, could have shot both sensors at once. I am having a simliar problem neal, with the same codes. I have checked and rechecked vacuum lines and the only broken one was the one that made the a/c come out the defrost and I fixed it. But I am sitting here with an expired tag and a damn CE light that refuses to go off.

 

HI!... O.k changed 02's with two old ones I had and no change. Then cleaned the new ones and no change. I've had 2 mechanics look into and they are both stumped too. JMC is coming over later with his scanner due to it goes way more into depth than the simple X-CAL2 does. If it doesn't pick up anything else then I'm going to tear the top end down and do a compression test. If that works out O.K then I'm going to clean the injectors. If that doesn't work then I'm totally stumped and what it's doing doesn't make sense.....................

 

I bet it's one his COP's, Searching my own threads & posts there was a time when I received the same code's - same problem P0171, PO174 , you know , those misunderstood codes. It wasn't until further down the line I started getting misfire codes. Everything went away when I replaced all the COP's.

Good Luck Neal