Ford Explorer Ecoboost 3.5 P0171/P0174

Hi I have a 2014 ford explorer 3.5 ecoboost it has about 55000 miles (125000km) on it never been abused was a executive car bought it with 47000 miles on it. When I purchased it it had no codes or at least that is what I thought it did when I scanned it it had a permanent lean code P0171 /P0174 lean on both banks. When I purchased it it had no warranty I did but it from a ford dealer was leased and had all the service records in the glove box I went through them and discovered they knew about the codes erased them so none was the wiser. On the service slip it said they looked but found no problems probably cleared the codes hoping it would reset and no codes would be present guess they were wrong. My STFT are about +3-+5 both banks LTFT are about +28.6-+29.5 both banks however the STFT's fluctuate like crazy sometimes they go as high as +20- then other times they go as low as -15 then some days they just hover around 0 to +/- 3 then next time I drive they are all over the place again my LTFT still stay around +28.6 to +29.5. I have reset the KAM but then the STFT are around +6 at an idle to +25 on acceleration. When the ECU has learned the STFT's are back around 0 to + / - 3 at and idle to around +5 under load with the odd time hitting + 12 both banks. LTFT finally hit their set threshold at trip the CEL again throwing P0171/p0171 codes. I have been told vacuum leaks don't show up on a ecoboost engine because the air is not metered with a MAF sensor rather with a MAP system thus the ECU adjusts for the difference in manifold pressure. Anyway I have checked all vacuum hoses just in case, smoke tested everything, changed all plugs and new coils, changed all 02 and A/F sensors changed map sensors checked fuel pressure running 60psi at an idle. I have noticed when I snap the throttle the fuel pressure dropped about 10 psi then recovered but hunts for the idle a bit after.I unplugged the fuel rail pressure sensor and the pressure increased to 70psi so that seems to be working. I tested PVC system and EVAP purge valve it holds vacuum. I left the gauge on and shut the car off while watching fuel pressure nothing dropped so that rules out leaky injectors. The vehicle pulls like hell lots of power no hesitation so that kinda rules out clogged injectors. I have had it to 2 shops they can't pinpoint the problem but not going to spend hundreds and hundreds for some so called tech to wiggle hoses when I can or have done exactly what he has done just to turn around and tell me the car has a lean condition I know thats why I brought it to you. If anybody out there can paint me in the right direction that info would be greatly appreciated. I have purchased a used solus pro to help narrow it down but could do with a bit of advice. I am very mechanically inclined worked on cars and bikes all my life built 2 race bikes and a 700hp mustang cobra but this has really stumped me thanks for helping out

You sure this thing doesn’t have a mass air flow sensor? I can find them on rock auto so for the 3.5 ecoboost turbo. Should be a connector right by the air filter. The symptoms are saying maf sensor. Have you checked fuel quality?

No it doesn't have a maf sensor all that in the air box is an IAT intake air temp sensor no MAF wish it was that easy

also fuel quality use 91 octane no ethanol

The 2 liter uses a MAF but not the 3.5 had that discussion with the parts dealer when I asked about the map sensor he said it had a maf sensor then realized he was looking at the 4 banger saw it only had a iat sensor

I’ll check all data tomorrow for possible technical service bulletins. Maybe a reprogramming.

Thanks I have a tune in it does the same as stock but it might need that

roggie13 wrote: Hi I have a 2014 ford explorer 3.5 ecoboost it has about 55000 miles (125000km) on it never been abused was a executive car bought it with 47000 miles on it. When I purchased it it had no codes or at least that is what I thought it did when I scanned it it had a permanent lean code P0171 /P0174 lean on both banks. When I purchased it it had no warranty I did but it from a ford dealer was leased and had all the service records in the glove box I went through them and discovered they knew about the codes erased them so none was the wiser. On the service slip it said they looked but found no problems probably cleared the codes hoping it would reset and no codes would be present guess they were wrong. My STFT are about +3-+5 both banks LTFT are about +28.6-+29.5 both banks however the STFT's fluctuate like crazy sometimes they go as high as +20- then other times they go as low as -15 then some days they just hover around 0 to +/- 3 then next time I drive they are all over the place again my LTFT still stay around +28.6 to +29.5. I have reset the KAM but then the STFT are around +6 at an idle to +25 on acceleration. When the ECU has learned the STFT's are back around 0 to + / - 3 at and idle to around +5 under load with the odd time hitting + 12 both banks. LTFT finally hit their set threshold at trip the CEL again throwing P0171/p0171 codes. I have been told vacuum leaks don't show up on a ecoboost engine because the air is not metered with a MAF sensor rather with a MAP system thus the ECU adjusts for the difference in manifold pressure. Anyway I have checked all vacuum hoses just in case, smoke tested everything, changed all plugs and new coils, changed all 02 and A/F sensors changed map sensors checked fuel pressure running 60psi at an idle. I have noticed when I snap the throttle the fuel pressure dropped about 10 psi then recovered but hunts for the idle a bit after.I unplugged the fuel rail pressure sensor and the pressure increased to 70psi so that seems to be working. I tested PVC system and EVAP purge valve it holds vacuum. I left the gauge on and shut the car off while watching fuel pressure nothing dropped so that rules out leaky injectors. The vehicle pulls like hell lots of power no hesitation so that kinda rules out clogged injectors. I have had it to 2 shops they can't pinpoint the problem but not going to spend hundreds and hundreds for some so called tech to wiggle hoses when I can or have done exactly what he has done just to turn around and tell me the car has a lean condition I know thats why I brought it to you. If anybody out there can paint me in the right direction that info would be greatly appreciated. I have purchased a used solus pro to help narrow it down but could do with a bit of advice. I am very mechanically inclined worked on cars and bikes all my life built 2 race bikes and a 700hp mustang cobra but this has really stumped me thanks for helping out

Exact same problem here and steps i took. 2015 Explorer sport with 99k miles. With that said and according to ford parts web site there are 2 map sensors. One on top of intake manifold (Part #: CX2619 (9F479) ) and other one is right in front of throttle body (Part #: CX2594 (9F479)). I am about to try both of them next week. Have you tried both of them?

Thanks,

Hi I already changed the top one on the intake no change but the one in front of the throttle body is a boost pressure sensor the one on the top is about $27 but the one in front of the throttle body though ford doesn't call it a map sensor though we both know it is its $300 here in canada if you do change it please keep me posted changed almost everything

I am going to try it as well though I don 't get a code it could be the problem because it is measuring air that is going through it once the throttle plate is cracked open

I looked at that as well after your post last night ford in Canada says $380 Canadian but found it on rockauto for about $90 Canadian so I bought it went out this morning. You are right it must measure the airflow going into the throttle body there is no MAF sensor so it has to measure air flow some way I have no idea why ford calls it a boost pressure sensor there is no boost on idle only vacuum probably so they can charge more. I did install a tune its crazy quick now and that was changing the map sensor on the top of the intake from a stock 2 bar to a three bar (can only be done with a tune though) other posters on explorer forums say that the map before the throttle body is a three bar but I compared the one i got with the tune and the throttle body one and it has a square raised spot on it the one I ordered with the tune doesn't so its not a normal map sensor. I wonder if it works like a MAF senor in conjunction with a MAP sensor so it can read pressure as well as air flow going to try it since I did a smoke test and can't find any vacuum leaks and like you low miles on it can't see it being injectors especially being lean on both banks and having good fuel pressure make no sense let me know if you find out before I do it will be a week before I get mine hopefully it solves the problem and get those fuel trims down. Mine always seems to trip the CEL after I get on it then I come up to a light idle for a bit then the light comes on. Sensor only sets a code when its broken not if it has issues reading a value

Waiting for my part to come in. I will definitely post my findings.

Mine is scheduled to be delivered today I to will keep u updated

Late reply here. Been busy. These parts did not solve my problem. Did you manage to solve your issue? If so, how?

Thanks,

Sorry been busy as well. I changed it as well didn't fix my problem either I think it might be a leaky intake gasket going to change that out when the weather is better could be partly clogged injectors as well or fuel filter(in tank) so I will start with the gasket and go from there since its the cheapest repair keep you posted keep me posted as well thanks if you want to ask me any more message me just on my way out thanks

Hello everyone,
Thread is 2 years old. Finally solved the issue in regards to P0171,174.

Replaced all 6 injectors. Fuel economy improved too after replacement. Injectors were nasty and they looked clogged.

Hopes this helps some of you.

Thanks for the follow up! Glad to hear it got fixed.