P0172 too rich bank 1, where to look.

Discussion in 'The Garage' started by NJjeff, Feb 11, 2014.

  1. NJjeff

    NJjeff Long timer

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    Car is a 03' Hyundai Accent 1.6L. 104K miles

    CEL is on.
    Code is P0172, too rich bank 1. (I'm guessing forward O2 sensor picked that up?)

    Sometimes when accelerating from a slow speed, low RPM's (car is a stick) it will loose power. Feels like it's running out of gas. Back off a bit & let it gently accelerate than at a bit higher RPM it will accelerate smoothly.

    My code reader gives a freeze frame.

    So when it threw this code.
    45 MPH
    185deg. water temp
    2160 rpm
    12.4 in Hg
    10% load
    L.T. fuel trim -23.4%
    S.T. fuel trim -25%

    Looks like it's trying to lean things out. Do I read that correctly?

    Fuel filter changed last year.
    This car does not have a mass air flow sensor so nothing to clean.
    MAP sensor was replaced few years ago under warranty.

    Looking online it's pointing to possibly O2 sensor. I hate to throw parts at a problem.
    With the software I can (will try it tonight) look at the real time O2 sensor output.
    So is it possible to tell a bad O2 sensor with the car just idling, or running on the highway? It's running normal in all other cases.
    #1
  2. fast4d

    fast4d Long timer

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    air leak in exhaust before O2 sensor?
    #2
  3. Wasser

    Wasser Spilt my beer

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    Try this LINK

    Best thing is its free!! :clap
    #3
  4. NJjeff

    NJjeff Long timer

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    The general public can sign up to that?
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  5. Wasser

    Wasser Spilt my beer

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    Yup! :D

    Hyundai is the only manufacturer that does not charge any fee for service information to "joe customer" :D
    #5
  6. NJjeff

    NJjeff Long timer

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    The cat on this car is part of the manifold. The front O2 sensor threads right into it. I'm quite positive there are no leaks.
    #6
  7. Wasser

    Wasser Spilt my beer

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    Air leak after combustion chamber would not cause this code to set. Fuel trim is being driven negative.
    #7
  8. big-t

    big-t Been here awhile

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    Unplug the front o2 and see if it cures the running problem.If not reconnect and clear code.
    Also check the fuel pressure regulator.if its a vacuum type there should be no fuel in the hose
    #8
  9. showkey

    showkey Long timer

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    Where are you guys getting this is free...............$20.00 per one week session.:deal:deal
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  10. freetors

    freetors Been here awhile

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    Can your code reader give you sensor voltages? It's always good to check that sensors are genuinely reading as they should.
    #10
  11. aardschok

    aardschok Fallout Rider

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  12. NJjeff

    NJjeff Long timer

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    Regulator is in tank. I's a return-less fuel system, 1 line up to fuel rail.
    I could try to unplug the O2 sensor but the car does run fine in all other conditions.

    To clarify it will only go low on power when re-accelerating.
    Perfect example, it occurs every day to work.
    Slow down from ~35 MPH, downshift and right turn 90deg. on to interstate entrance ramp. It's a tight turn so I go into second gear. It will not have much power so I have to very slowly allow it to build RPM. Once at 2500 rpm (guessing because it has no tach.) it will smooth out and normally accelerate. Now don't jump to conclusions it will do this making left or right turns at any location.
    Odd though as it will accelerate from a standstill normally. It will accelerate at highway speeds normally.
    As I'm thinking and typing this it's always after a brief slowdown and downshift where it feels like it's running out of fuel, and yes I just got gas today. Fuel tank level has not made a change.
    #12
  13. NJjeff

    NJjeff Long timer

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    Yes it does. My code reader plugs into a laptop so tomorrows trip to work it's going to be my passenger.

    I think it can record a few sensors data over a trip. If so I'll record front O2 sensor and (as I have read online) MAP sensor readings.
    #13
  14. NJjeff

    NJjeff Long timer

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    Ok ran the OBD reader with live data during drive to work. Oddly enough the car ran nearly perfect today. Only a slight power loss at one moment.

    Anyway few things I noticed.

    The software can give live data along a moving chart for 2 sensors. It can record data for any sensor selected. I think up to 10 at a time. Trouble is I forgot to press record.
    I did watch (when I could) the real time data.
    First I selected O2 sensor 1 and short term fuel trim.
    Car parked in garage. Outdoor temp. 4 deg.
    Within I'd say a few minutes the O2 sensor very quickly began to oscillate between .85 v and .03 v. Values were slightly changing but the high and low centered around those numbers. It switches quickly, I'd guess like 2 cycles per sec.
    The short term fuel trim readings are around -2% to 2% when holding a steady speed on flat ground at around 35 mph. the graph makes a wiggled line. If I accelerate or decelerate the trim seems to follow.

    I decided to try several sensors.
    Water temp (when at normal gauge reading) 185 deg.
    Throttle position appears to follow correctly. No "noise" along the graph.
    I switched to Intake air temp after about 20 minutes of driving. it was 21deg. By that time it was around 8 deg. outside.
    Ignition timing seemed to vary with load. Most I saw was 26 deg. of advance.
    MAP readings clearly followed throttle position but seem inverse of my thoughts. Heavy on the throttle gave readings of 24 to 26" Hg. Closed throttle going down hill gave 7" of Hg. Steady state 65 MPH level road was around 15~17". Idle around 10.3"
    Rear O2 sensor switched slowly from .8 (something) to .03 (something). Frequency was several seconds before a change.

    Only odd thing I noticed is at times the short term fuel trim would drop to -23%. I'll try it again tonight to see if it stumbles and where the fuel trim goes.
    This time I'll press record.
    #14
  15. Wasser

    Wasser Spilt my beer

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    First red flag I see. That is if the readings are correct on the scan tool.

    Heavy throttle should= lower number (less vacuum, closer to atmospheric pressure)

    Closed throttle= higher number (high vacuum)

    Normal engine is ~17-22 in. hg at idle. As the throttle plates open, the numbers should start dropping. It looks like yours are going higher. Especially at closed throttle down hill. You should have a very high vacuum reading.

    I'd throw an old school vacuum gage on it just to compare readings.

    Since your vehicle uses a MAP, it is a speed density system. MAP is a key input for a speed density system. It is used to calculate engine load.

    Your readings seem totally out of wack. Could be the scan tool. That is why I would try a "old school" vacuum gage just to compare.
    #15
  16. C Squared

    C Squared Now with TURBO!

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    Yup. You need to figure this out. values seem wrong.
    Any time you are double digits on STFT you have a problem. STFT is based mostly off the O2 sensor. It could be right and ECM is trying to correct.

    ? EGR valve. Maybe a part of the problem. But your data doesn't show this.
    PCV valve ?

    I'd need to have it in font of me to be a real help. With a scan tool I like and trust.
    #16
  17. NJjeff

    NJjeff Long timer

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    Agreed, seemed backwards to me also. But I posted it because I thought well maybe I'm not seeing it correctly.

    The software is OBD.com. It consists of a OBD connector X USB cable and software. I have it loaded on a laptop so I could take it into the car.

    I glanced down several times while driving on the interstate. I lifted and values went down????? I nearly floored it and it went up high?????
    I tried different sensors and came back to the MAP yet same results. The values are off the map sensor with the units " of mercury.

    I'm going to e-mail the company this question.

    The MAP is a combination intake air temp / MAP. It was replaced a few years ago when the CEL came on with a intake air temp. out of range error. Sensor replaced and all was fine.
    #17
  18. b1pig

    b1pig Been here awhile

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    snip from this website: http://www.obd-codes.com/faq/fuel-trims.php



    dont over diagnose it. a bad O2 can cause the computer to compensate for a non-existant problem. if you can troubleshoot the O2 sensors, do that first.

    depending on how many miles are on it, a new O2 sensor might be a good idea anyway. using fuel additives can also cause funky readings on some systems. (dodge neons were notorious for this)
    #18
  19. boasjohn

    boasjohn Adventurer

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    A lot of time the map reads backwards, not a vacuum sensor but a manifold absolute pressure sensor . Check map with koeo ( key on engine off) see what it reads then start car and see what it reads. Like 29 koeo and 11koer ( key on engine running) 29 - 11 = 18 in of vacuum good luck
    #19
  20. 1911fan

    1911fan Master of the Obvious

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    I'd guess vacuum leak. Can affect fuel trim and might account for the lag as well.


    1911fan
    #20