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CEL P0171 Lean Bank 1

Posted by bigdog225, Sep 6, 2008
Newbie Forum - Beginner DSM modification questions and discussions. Common, repetitive, and general discussions will get dumped here from other tech forums. Unless you're a Probationary member you shouldn't post threads here.

  1. bigdog225

    bigdog225 Probationary Member

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    Houston, Texas
    99 Eclipse GS N/T

    History - Car over heated. Replaced water pump, timing belt, radiator, resurfaced the head, bought all new gaskets. Drove for 2 weeks and was sometimes dying at stops and had a rough idle. Then and the timing belt tensioner pulley bolt broke. Replaced it, replaced timing belt again. Started rigth up ran fine for about 2 miles then CEL P0171 and very rough ride and sometimes dying at stops. Very noticable smell of fuel from the exhaust which was not expierenced after the first round of fixes. All the searches I did talk about turbos. Mine is a Non Turbo. Any help is GREATLY appreciated. I am so ready to just drive and enjoy.....Thanks again
    #1
  2. BoredDSM

    BoredDSM Proven Member

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    Code mostly associates with your o2 sensor reading lean but if it is lean then you shouldnt be smelling gas. Clean out your maf cause it gets dirty and prevents correct readings when you use reusable filters that you spray oil on. Also an unplugged or vaccum leak can give you the P0171 code. Make sure you checked your timing. Very unlikely but you could of had the timing off and the marks on the pistons are heating up and causing pre detonation but you would most likely have bent valves already.
    #2
  3. mentalTSiAWD

    mentalTSiAWD Proven Member

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    :confused:
    You did plug your O2 sensor in the manifold back into the harness when you reassembled everything didn't you?
    #3
  4. bigdog225

    bigdog225 Probationary Member

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    Houston, Texas
    MAF is good. 02 is plugged in. Ill check for a vacuum leak now.....
    #4
  5. link16

    link16 Proven Member

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    Last I checked....2gnt's dont have MAF's so having a clean one might be your problem....LOL. I would pull the spark plugs and see what color they are, otherwise I would pull and clean your o2 to make sure it is getting a good reading and not just clogged.
    #5
  6. TALONTRAX

    TALONTRAX Proven Member

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    The 420a motor is the same as a Neon . . . The throttle body is at the end of a rubber snorkel, effectively making the rubber snorkel section part of the intake manifold, & I have seen them dry out & develop cracks leading to air/intake leaks . . . check it out . . . :talon:
    #6
  7. Project2G

    Project2G Proven Member

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    Littleton, Colorado
    Perhaps this will help..
    [​IMG]
    #7
  8. bigdog225

    bigdog225 Probationary Member

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    Houston, Texas
    Finally this thing is fixed! Replaced the Bank 1 O2 Sensor and all is good again. Went ahead and replaced the Bank 2 O2 because it had never been done. Shes runnnin great again :sneaky:
    #8
  9. sdsdsd

    sdsdsd Proven Member

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    Chicago, Illinois
    Looking for ideas guys.

    I have this code on my car appear for a few days now. I clear it and it comes back after couple days. I have not noticed any performance impacts or any issues with the car driving. I have a 2GNT 98.

    Any ideas? thanks.
    #9
  10. sdsdsd

    sdsdsd Proven Member

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    bump to the post.

    I'm still seeing the code come and go. I've checked my o2 sensors with my scanner and it says that those are all ok.

    I do get a freeze frame in the cpu and I'm not exactly sure how to read it. but one of the fuel trim values doesn't look right.

    Any tips?
    #10
  11. Spln_Hrd

    Spln_Hrd Proven Member

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    Hastings, Nebraska
    I doubt your maf sensor is good on a n/t your car uses a speed density system which uses a manifold absolute pressure sensor and a throttle posistion sensor to calculate airflow.


    to sdsdsd:

    If you have access to a scan tool look at your long term fuel trim with the car idling for a few minutes and see if it goes above 10%. Do this cold and hot.

    Then with the engine warmed up run the engine at about 2500 rpms for 5 minutes and see what the fuel trims are doing is they normalize you more than likely have a vacuum leak, because vacuum leaks ofset the airflow alot more at low loads.

    After you have done this mash your gas pedal to the floor and release it immediatly, after the release your o2 sensors should both read high. That is a good indication that they are working properly.
    #11
  12. sdsdsd

    sdsdsd Proven Member

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    My scan tool won't show me live readings. Its an Actron cp9175 i think is the model number. I can see what the fuel trim is through at the time that the code was thrown because it creates a freeze frame.
    Per the sensors it shows that the o2 sensors are both ok. I'm thinking its prob a vaccum leak and those I know are a pain to find :(

    I'll keep you posted. thanks for helping!
    #12
  13. sdsdsd

    sdsdsd Proven Member

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    Chicago, Illinois
    Finally did some scanning in my car since i didnt drive it for a bit.

    Some of the stuff i pulled with my scanner from the freeze-frame the code was tossed at:

    Engine RPM: 832
    Load Value : 4.7%
    MAP Sensor: 43KPA
    Coolant temp: 163 degrees Fahr
    Long Term Fuel Trim 1 : 24.2 %
    Short Term Fuel Trim 1: -100.6%
    Fuel System 1: CLSD
    Fuel System 2: N/A %
    Vehicle speed: 0 MPH

    I'm not sure how to interpret this info. Does anyone with more experience know more about how to interpret the code?

    Funny thing is when i clear the scanner it is random how quickly it comes up.

    thanks.
    #13
  14. sdsdsd

    sdsdsd Proven Member

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    Chicago, Illinois
    bump
    #14
  15. cgmtboarder

    cgmtboarder Proven Member

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    i have a 95 eclipse n/t and it has been doing the exact same thing as the OP. rough idle and acts like it wants to die and it sputters alot. and finally after 4 months i got the check engine P0171. so im gonna change the bank 1 o2 sensor and hopefully that fixes it.
    #15
  16. Project2G

    Project2G Proven Member

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    Littleton, Colorado
    This may help.
    [​IMG]
    [​IMG]
    #16

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