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Poor fuel economy and fuel system error

Discussion in 'Stock 2011 - 2019 Ford Explorer Discussion' started by Sammy76, October 9, 2018.

^^Searches ExplorerForum.com^^





  1. Sammy76

    Sammy76 New Member

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    I recently purchased a 2013 XLT 3.5 to replace my 03 expedition. I need something with better mileage than the beast. Anyway, when I bought it the average economy was around 20mpg. A couple days after that I started noticing that the economy was dropping to around 13mpg, the same as the expedition! And it also started idling rough.
    After realizing this I hooked up my scanner and forscan, I noticed that the fuel trim is running on the rich side with the ltft being between -3 to-5 and the stft anywhere between 4 to as far off as -26 for both banks. The odd thing is that when monitoring the fuel system to see if it's in open or closed loop bank 1is in closed as expected but bank 2 says error!

    Now, I discovered that the previous owner had never changed the plugs or coil packs, it has 120k on it! I plan on replacing all the plugs and coil packs as well as the pcv valve. My question is what would be causing the error on bank 2? Would it be a bad injector or fuel rail? Obviously fouled plugs would affect the gas mileage but badly enough to drop the economy to 13 mpg highway? Any help would be appreciated as googling has gotten me nowhere as far as the error.
     
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  3. peterk9

    peterk9 Staff Member Moderator Elite Explorer

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    What is the error code you're getting? It seems this is not a new issue here.


    Peter
     
  4. Sammy76

    Sammy76 New Member

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    No code is being set. Oddly enough even with the short term fuel trim hitting -27.
    I discovered the bank 2 error while monitoring the system in forscan.
    Both pre cat o2 sensors are behaving as expected which is why I'm unsure what the problem would be.
     
  5. peterk9

    peterk9 Staff Member Moderator Elite Explorer

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    You could try disconnecting the battery for 10 minutes or so. That will result in a transmission relearn as well as fuel and idle trim. It is in the Manual under Battery Relean.
    When the battery is disconnected or a new battery is installed, the engine must relearn its idle and fuel trim strategy for optimum driveability and performance. To begin this process see page 350 of the 4th printing of the Manual. Not sure if that will do anything for you.
    Also, your profile shows 97 Explorer. Time to update.

    Peter
     
  6. sheltonfilms

    sheltonfilms Active Member

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    No code? With that high of a negative fuel trim it should be. Can you do some screen shots of your O2 sensors while showing the STFT (graphing mode) What is LTFT for that bank?
     
  7. Sammy76

    Sammy76 New Member

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    Here ya go, I didn't have the fuel system module selected here as I was mostly trying to verify that the O2 sensors were functional. And here's another one showing the fuel trim and fuel system error. Screenshot_20181009-111802.png Screenshot_20181009-112213.png
     
  8. Sammy76

    Sammy76 New Member

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    Yeah, I had to sell the 97 when I found out we were expecting as I had to have 3rd row seating.
    I did stay Ford though lol. Picked up the expedition for cheap as it needed a new intake.
    As far as the battery procedure, would they have done that when the tsb for exhaust gas in the car was done? If not I'll give it a go and see if it helps.
     
  9. sheltonfilms

    sheltonfilms Active Member

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    You got the wrong PIDs up for the upstream precat O2s (O2S11 and O2S21). You are reading the heater circuit current (notice it is in mA). You need to pull the signal voltage.
     
  10. Sammy76

    Sammy76 New Member

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    I didn't even notice that. I will recheck as soon as my wife gets back with the car. Thanks for pointing that out.
     
  11. Sammy76

    Sammy76 New Member

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    Ok, so apparently the fuel system 2 error isn't an error. While searching for where the O2 sensor pid would be located in forscan I stumbled across a post on the forscan forum. In their infinite wisdom Ford handles both fuel banks as one system. The error was just forscan saying that it's not there. Strangely enough whenever I googled fuel system bank 2 error it only gave me results for the O2 sensors. Googling O2 sensor bank 2 lead me to the post regarding the error.

    I'll leave this post as I found another here regarding this issue that was never updated.
    Off to order the plugs and cop's then bed.
    Thanks for the help guys :)
     
  12. sheltonfilms

    sheltonfilms Active Member

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    Oh yeah fuelsys just shows if you are in open or closed loop.

    Still need to look at why your STFT are pegging negative.
     
  13. Sammy76

    Sammy76 New Member

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    I will, honestly I'm not sure if it's sleep deprivation or the old age catching up but I can't find any other pids for O2 sensor volts or fuel trim other than the ones labeled as sensor 2 in each respective bank. I'll check again tomorrow and get back to you, hopefully I can get this sorted. ATM I have a 15 month old teething and a 2 and a half year old who's currently sick.
     
  14. KayGee

    KayGee Well-Known Member

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    I don't think you will get any codes until LTFT exceeds the preset threshold (could be up to + or - 20-25%, not sure for Explorer).

    Are your STFT same at idle as they are at 2K or 3K RPMs?

    If plugs and COPs were not changed in 120K miles and you aren't getting any misfire errors, that is pretty good. You may want to check the plug gap and confirm if it is in spec.

    May want to check compression and fuel pressure (leakdown).
     
  15. Sammy76

    Sammy76 New Member

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    Thanks for the reply, I had believed that the combined fuel trim over 20% was enough to trip a code. As far as the fuel trim, no they are higher at idle I believe. I don't have the tools or available work space for more in depth testing. Unfortunately we were rear ended by an apparently uninsured motorist on Friday and have been fighting with insurance to pay for transmission work.since the accident it's been shifting hard and occasionally not shifting till it's over 4k RPM. Prior to the accident I had the vehicle checked by a shop for anything that needed work as well as having the dealership do the exhaust fix and both stated no other obvious problems. Insurance is fighting paying for anything. Accordingly any further testing and repairs of the fuel system have been put on hold for now.
     

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