2000 Ford Lightning P0171 AND P0174

it would be nice to look at mode 6 data....need a scan tool with that capability...$21 isnt going to tell you anything.there is tids and cids....test ids and components ids.what are your 02 sensors doing?your fuel trims are little better at idle?have to watch you dont kill your cats.most of the time dirty maf/low fuel pressure/vacuum leaks.take for a test drive and at wot look at your 02 and see if it goes full rich.can you graph 02 sensors?if it doesnt disconnect maf and see what happens.fuel pressure good snap throttle?no bleed down?

I will look over your 'christmass list' BUT would ask vehicle is STOCK- nothing done added changed? History- what is the fuel pressure? in psi.. will need more BUT I believe $21 is EVAP system...any other codes? can you read the higher codes P1xxx type? anyway that is a place to give a general look - purge?

autojoe wrote: it would be nice to look at mode 6 data....need a scan tool with that capability...$21 isnt going to tell you anything.there is tids and cids....test ids and components ids.what are your 02 sensors doing?your fuel trims are little better at idle?have to watch you dont kill your cats.most of the time dirty maf/low fuel pressure/vacuum leaks.take for a test drive and at wot look at your 02 and see if it goes full rich.can you graph 02 sensors?if it doesn't disconnect maf and see what happens.fuel pressure good snap throttle?no bleed down? When MAF is disconnected, LTFT drops to 0.00 and STFT sits at about 4.0 in Idle. When MAF is reconnected, the truck spends time relearning then maxed out again. Keep in mind, the MAF is brand new. I'm assuming that when you unplug the MAF, that the truck just falls into default mode and thats why it drops to 0 for LTFT My LTFT is worst at idle but gets better with even just 200 rpm added or removed from the idle RPM's Fuel pressure is good and truck does not surge or stumble in WOT or idle. The only notable symptoms of the truck are CEL keeps coming back on and LTFT is maxed out at %25 in idle and some various different cruising rpm's/speeds. Regardless of what rpm or engine speed, the LTFT never 0's out. It is always sitting in the positive side of the scale. kev2 wrote: I will look over your 'christmass list' BUT would ask vehicle is STOCK- nothing done added changed? History- what is the fuel pressure? in psi.. will need more BUT I believe $21 is EVAP system...any other codes? can you read the higher codes P1xxx type? anyway that is a place to give a general look - purge? Test $21 is the only one that comes back as fail. Everything else is a pass. Truck is bone stock. I can't recall the results of the fuel pressure test in numbers but do recall it being just a touch low from factory spec whether key turned on without engine running, engine running in idle or engine in WOT. By low I mean maybe 1 to 2 psi off. O2's are jumping back and forth rapidly over and under the spec millivolts as they should. They also max at .9 millivolts when carb cleaner is sprayed into a vac line. I pulled every vac line connected to the intake and plugged both ends of the hoses to look for any change in the LTFT. No change noted. Still maxed at 25% in both banks. Going to the scrap yard today to grab a DPFE sensor. Its the only sensor that could be related to this issue that I haven't changed. Its a long shot, but i'm grasping at straws now.

Some thoughts- Fuel pressure is to CRITICAL for guess ' a little low A little pregnant. ... get a fuel pressure gauge- post readings. Then remove and plug vac line to fuel pressure reg - did PSI increase and STFT change? You should be able to unplug vac lines at DPFE checking for lost vacuum. There are NO exhaust leaks, issues?

Disregard your long term fuel trims for a few mins. Use your pressure gauge when the vehicle is being driven under load! Does it still stay just a little bit below spec or drop further? Under wot will the upstream 02's read .9 of a volt. Compare stft with the maf plugged in and unplugged! Alot of times on those engines the vaccum leaks don't show up by spraying and listening to the idle! You may see it swing on the fuel trim when spraying and it may be more obvious when the engine is ice cold! What brand of new MAF?

Well I have maybe an interesting development. Could be something or could be nothing at all. When I run the truck and unplug the MAF, the LTFT drops to near normal or negative values. The lowest I have seen was -12% in idle only. Hit the gas pedal and it levels out nicely For a bit, the LTFT sat at "0" with STFT sitting at 3.4 with the MAF unplugged and I took it for a drive without the MAF plugged in. It ran awesome. The shift points on the Transmission were crisp and seat lurching. Felt more power in the truck then I ever have before. It leads me to ask if the MAF I bought is programed for the Lightning or just a Triton 5.4. Is there anyway I could find out? Then as soon as I re plug it in, it maxed out again in the positive zone and runs like crap stumbling on accel or throttle as it "relearns" off the MAF. The relearning process seems to take forever. It will even switch the system to open loop sometimes cause its running so crappy while learning. I never had this issue with my old MAF if I had to pull the battery of relearning stumbling and hesitating. I'm really starting to suspect my new MAF..... is junk

i would suspect the maf.where did you buy the maf?did they give you the right one?

autojoe wrote: i would suspect the maf.where did you buy the maf?did they give you the right one? I bought it from Parts Source. I'm really debating that question myself. In 2000 or 2001 Ford changed the MAf from a 80mm to a 90mm. The question is, was I suppose to get an 90 but got an 80 instead or vise versa?

Take a copy of the VIN to your local ford dealer - assuring the correct quality part.

there is a tsb for p0171 and p0174 .The Malfunction Indicator Lamp (MIL) may illuminate and Diagnostic Trouble Code (DTC) P0171 and/or P0174 may be stored in memory on some vehicles. This condition may occur when the vehicle is at an idle and/or neutral condition particularly at higher altitudes and while using ethanol blended fuel.Reprogram the Powertrain Control Module (PCM) with new calibration. Check for correct fuel pressure. Check for induction air leaks. Check for PCV system leakage. Reprogram Powertrain Control Module (PCM). the maf oem part number for your truck is XL3Z12B579BARM.