Dismiss Notice



Register Today It's free! This box will disappear once registered!

Poor idle, NO power

Discussion in 'Stock 2002 - 2005 Explorers' started by JW, April 22, 2017.

  • Searches ExplorerForum.com
    1. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

      Joined:
      May 26, 2009
      Messages:
      10,433
      Likes Received:
      96
      Trophy Points:
      78
      City, State:
      Greenville, SC
      Year, Model & Trim Level:
      00 Sport FI, 03 Ltd V8
      Your pre-cat O2 sensors are good. Bank 1 sensor 1 varies between 0.06 and 0.86. Bank 2 sensor 1 varies between 0.05 and 0.855. On my PCM strategy if the PCM determines one bank sensor is bad it will utilize the one good sensor for both banks. It is obvious when this happens since the STFTs for both banks will always be identical.

      The PCM primarily uses the MAF sensor airflow to calculate load. For your data log the load seems to be proportional to the MAF sensor reading. In general the MAF sensor reading increases and decreases with engine speed and with TPS voltage.

      I think the significant issue is that both bank LTFTs slowly change but increase significantly with load but the STFTs rapidly change a small amount. This puzzles me. I'm considering there may be a sensor wiring error. I suggest that you disconnect the sensor connector that is easiest to access. The PCM should detect a sensor heater voltage error and set the corresponding DTC. Read the code and see if it corresponds to the sensor that was disconnected. Remember that bank 1 is the bank that contains cylinder 1 (engine front/passenger side in USA). Sensor 12 is the bank 1 post-cat sensor and sensor 21 is the bank 2 pre-cat sensor.
       
      Last edited: May 7, 2017
    2. Support EF

      Join the Elite Explorers for $20

      Explorer Forum has probably saved you that much already, and will continue to save you money as you learn how to diagnose fix problems yourself, and learn which modifications work without having to experiment on your own. Elite Explorer members see practically no ads, can add their own profile photo, upload photo attachments in all forums, and Media Gallery, create more private Conversations, and more. Join Today. Your support is greatly appreciated.


      to hide adverts.
    3. N4YLOR

      N4YLOR New Member

      Joined:
      May 7, 2017
      Messages:
      20
      Likes Received:
      3
      Trophy Points:
      13
      City, State:
      Maine
      Year, Model & Trim Level:
      2013 Ford P.I.U. 3.7L
      I know you said you took readings on the MAF and swapped it with a non motorcraft one, but I have a quick story anyway.
      Years ago I had a 99 super duty with a 5.4. I was driving along and all of a sudden the truck became gutless, would never stall, but I would put my foot right to the floor and it just wouldn't go. The check engine light flashed while this happened and then it would just clear up and the truck would be happy again. It wasn't long and it would happen all the time. It was so frustrating not having any guts to keep up with traffic and I would throw it in neutral and roar that truck thinking maybe I'd clear out some restrictions but nope.
      Went to the parts store and had them scan it for me. Came back as whatever the code is for possible MAF issue. Asked the kid at the parts counter to look it up for me, 100 bucks. He goes dude, save yourself some money and clean it with this stuff (CRC MAF spray). Gave it a shot and it didn't really do anything. Brought it to a local garage and they said 'your shift sensor is toast, we can swap it out right now, 250'. So I went with it. Left with the truck and it was okay for a couple days, then the issue came back. Went BACK to the garage they scratch their head and say leave it overnight. Call me up a few days later and say 'what have you been doing to this thing, the catalytic converter is all stuffed up no wonder it's got no guts!! Temp readings through the roof before the cat!' $700 for cat and new exhaust behind it.
      2 miles down the road, you guessed it. I start thinking and go back to square one and ask the garage 'you think it could be my MAF after all?' He says No way, not a chance, we checked the readings it was within spec blah blah blah(kind of like my story). So I said okay, if you're so sure then let's make a deal. You replace the MAF with a motorcraft. If that solves the problem, you pay for it, for bending me over on all these un-needed repairs. If it doesn't work, I pay for it. He said deal and guess who only had to pay 950 for a 100 dollar repair? Anyway the moral of my story is, your symptoms sound a lot like the MAF problem I had. Is it possible it really is faulty, and the car just doesn't like the aftermarket MAF you replaced it with? Could you try out a Motorcraft one and return it if it doesn't fix the problem?
       
    4. boominXplorer

      boominXplorer Elite Ranger Elite Explorer

      Joined:
      September 16, 2002
      Messages:
      8,187
      Media:
      55
      Albums:
      3
      Likes Received:
      253
      Trophy Points:
      103
      City, State:
      Virginia Beach, Va
      Year, Model & Trim Level:
      00 4x4 Mounty
      Check your o2 sensor wirering side to side for the front o2s. Make sure you don't have the banks switched. It's easy to do since both o2 sensor wires come out near each other in the harness and have pretty long pigtails.
       
      Last edited: May 9, 2017
    5. JW

      JW Third Gen Collector Elite Explorer

      Joined:
      October 16, 2000
      Messages:
      347
      Media:
      12
      Albums:
      1
      Likes Received:
      30
      Trophy Points:
      28
      City, State:
      Valencia, CA
      Year, Model & Trim Level:
      A Pair Of Gen 3s
      boominXplorer - O2s are definitely not crossed over. Replaced them one at a time while the engine was out, so they were easy to trace.

      N4YLOR - still running the factory MAF and housing. I temporarily swapped in an aftermarket MAF and got the same results, so I went back to the original. (Not saying it's not *a* problem, but it doesn't seem to be *the* problem.)

      2000StreetRod - are you saying the LTFTs are not *proportionally* increasing with load? Does a higher percentage indicate rich or lean? (I think I've answered that with some research - lean.) And you're talking about disconnecting an upstream O2 sensor, correct? Do the downstream sensors play any role in tuning the engine?

      Also, I re-read an earlier post of yours while reviewing my datalog. You stated that anything over 5% indicates a lean condition. Most of my LTFTs in the log are well over 5%, except on the driver's side.
       
      Last edited: May 9, 2017
    6. corignelson

      corignelson New Member

      Joined:
      February 27, 2018
      Messages:
      7
      Likes Received:
      0
      Trophy Points:
      1
      City, State:
      sacramento
      Year, Model & Trim Level:
      1999 Explorer XLT
      Not sure if the issue is resolved(almost a year old), but it sounds like an intake manifold leak. Or a timing chain issue. The fuel trims indicate unmetered air in the exhaust stream and smoothing out with the throttle cracked supports that.
       
    7. corignelson

      corignelson New Member

      Joined:
      February 27, 2018
      Messages:
      7
      Likes Received:
      0
      Trophy Points:
      1
      City, State:
      sacramento
      Year, Model & Trim Level:
      1999 Explorer XLT
      Especially if it’s a plastic manifold, they tend to crack.
       
    8. JW

      JW Third Gen Collector Elite Explorer

      Joined:
      October 16, 2000
      Messages:
      347
      Media:
      12
      Albums:
      1
      Likes Received:
      30
      Trophy Points:
      28
      City, State:
      Valencia, CA
      Year, Model & Trim Level:
      A Pair Of Gen 3s
      Turned out to be a blown driver's side cat, which sent debris downstream into the secondary cat/resonator/whatever it is.
       
    9. corignelson

      corignelson New Member

      Joined:
      February 27, 2018
      Messages:
      7
      Likes Received:
      0
      Trophy Points:
      1
      City, State:
      sacramento
      Year, Model & Trim Level:
      1999 Explorer XLT
      That’s good info to have. I just bought a 99’ 4.0 sohc that needs a timing set at a minimum. If, after the rebuild, I experience these symptoms I will definitely take a look at the cats.
       

    Share This Page







    We Support Our Troops!