First thread on this site, so forgive me if I sound like an idiot. I recently purchased a 2005 XL 4.2L with very low miles (56K) and is in very good condition. I noticed that I get a slight shudder when stopped, other than that the truck runs like a dream. I pulled the codes with my OBD2 reader and codes P0171 and PO174 came up. I replaced the air filter, checked for vacuum leaks, replaced spark plugs, changed all fluids/ filters, cleaned throttle body and MAF sensor 2X, erased the codes and performed a reset, but the problem still persists. Going to order a new fuel filter today and replace that. Is there something that I'm missing, possibly clean the EGR valve? I tried to locate the IAC valve but to no avail, does this model have one? If anyone can point me in the right direction I'd be very grateful, I'm at a loss at this point. I'm thinking that I may need to replace the MAF sensor or fuel pump, but I'd like to get a second opinion on the matter. Thanks in advance, hope to hear from someone soon!

 

My guess FPDM
A common problem is corrosion is the Fuel Pump Driver Module. If you are a northern vehicle and you have not changed it before this is where you should look next. The FPDM is located above the spare tire and is held on by two (10mm ?) screws. Easy to change once the spare is out of the way. Remove the screws and look at the back side of the FPDM it is likely corroded to the point that the printed circuit board is exposed. Road salt eats it up. I am 95% sure a FPDM from a 2004-2008 Ford Crown Vic, Lincoln Town Car and a Mercury will fit and because they are mounted in the trunk (behind the back seat rt center) are unaffected by weather. If you purchase a new one, about $50-$80, it will come with rubber standoffs to prevent the dissimilar metal corrosion. Clean the ground connection.

 

Thanks, Jimboy. I ordered a new one today and it should be here by Monday. I also replaced the PCV valve, the vape canister purge valve and fuel filter, just for good measure. The truck's an '05, so I figure that it's time to replace a couple of things. Would you replace O2 sensors at this point, or should I just wait for them to fail? The damn lean codes are still popping up, but I'll figure it out eventually. If the fuel pump driver module doesn't work then I'm gonna go with the MAF sensor and O² sensors next.. Thank you for the help, I should've just listened to your advice first, but pride wouldn't let me. Lesson learned!

 

Unless you’ve tested those O2s and the MAF, you’re likely replacing good parts for warm fuzzies.

 

I'm beginning to figure that out at this point, even with replacing and cleaning parts, the problem seems to still be lingering. I'm no mechanic, still learning at this point. I no longer trust anyone else to work on anything of mine, no one will work on your things as well as you can. Last time I went to the mechanic I paid for something that they didn't even do, then just did it myself for a fraction of the cost. Time to buy a multimeter and a better scan tool I guess? Thanks for the info!

 

Let's refresh ourselves
Code P0171 Ford - "Fuel Injection System Too Lean Bank 1" Possible Causes

• Intake air leaks
• Faulty front heated oxygen sensor
• Ignition misfiring
• Faulty fuel injectors
• Exhaust gas leaks
• Incorrect fuel pressure
• Lack of fuel Faulty Positive Crankcase Ventilation (PCV)
• Faulty Mass Air Flow (MAF) sensor
• Incorrect PCV hose connection

Code P0174 Ford - "Fuel Injection System Too Lean Bank 2" Possible Causes

• Intake air leaks
• Faulty front heated oxygen sensor
• Ignition misfiring
• Faulty fuel injectors
• Exhaust gas leaks
• Incorrect fuel pressure
• Lack of fuel
• Faulty Positive Crankcase Ventilation (PCV)
• Faulty Mass Air Flow (MAF) sensor
• Incorrect PCV hose connection

"If the P0174 is combined with the P0171 code, the problem is likely caused by an intake leak or the Intake Plenum Gasket and seals."
In Post #3 you indicated that a new FPDM has been ordered. Install the new FPDM (clean ground wire and connection) and see if the codes will clear.
Make sure the MAF is properly plugged in and make sure all hose connections downstream of MAF and Throttle Body are tight. Look for tares in the intake hose. Look for any place that unmetered (bypassing MAF) air may be entering engine. The "incorrect PCV hose connection" should be checked and ruled out or corrected.

Keep us informed of your progress.

 

So I replaced the PCV valve, purge valve, FPDM, plugs, fuel filter, cleaned the MAF sensor again, checked for intake leaks, cleared the codes and they came back. I'm going to keep trying with replacing what I can because the truck is an 05 and deserves new/quality OEM parts. Like you stated, the FPDM was on its way out because I had the vehicle shipped down to Florida from Illinois. Next on the list are the upstream o2 sensors, EGR valve and MAF sensor. I may even purchase a smoke tester, I'll keep you posted, thanks for the detailed list. Does this vehicle have an IAC valve, I'm getting conflicting answers about it, some say yes, some say the model is a fly-by-wire?

 

every time you replace a part that hasn't been tested/diagnosed as failed, you are introducing another new variable and potential failure (i.e. bad new part and/or improper install).

admire all of the time/money/effort being spent but would encourage more testing/diagnostics and less shot gunning of parts.

 

You're right, leaning towards faulty injectors and/or intake manifold gasket at this point. I was doing the carb cleaner test last night and didn't find the vacuum leak yet. I was hoping to get lucky, but that's not panning out for me real well at the moment, was hoping for a miracle. Lol. I know that everything installed was done correctly and I used all Motorcraft products, everything that I replaced was very simple to do. Gonna get home later today and try to find the leak. The car runs great in the morning when it's cold, but after sitting in the heat and driving home I get a sputter. Thanks for the input, will keep you all posted! Would you invest in a smoke tester and multimeter? I've got a cheap obd2 scan tool to help, anything you'd recommend looking at first? Thanks again.

 

come to think of it, something strange did happen during the cold snap last week. While getting gas, the pump stuck from being cold and gasoline started coming out of tank, right under fill-up cap. So do you think that I could possibly have a leak under gas cap, causing the line to lose pressure? Just a thought, another thing that I'll check out after work. My Haynes guide came yesterday, so that should help a little, that and YouTube videos. Obviously I'm not a mechanic! Ha.