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Thread: Rough idle and running and some strange readings

  1. #1
    Join Date
    Feb 2019
    Location
    cyprus
    Posts
    5
    My Cars
    2008 118d se

    Rough idle and running and some strange readings

    Good afternoon guys,
    This is my first time on here and the first BMW I have actually owned and worked on. It is a 118d SE late 2008 model with the N47D20C engine.
    Just here is a little bit of history,
    When I got this car within a week I sent it off to have the Cam Chains replaced, While that was been done they cleaned my intake manifold and swirl flaps, Had a new Glow plug controller and 1 glow plug, while the car was in bits I thought might as well change the clutch and save me a penny on labour a bit down the line.
    So since having the car it has had a rough idle when cold but also a bit of a jumpy ride when trying to run along smoothly at 50kph, it did display any signs of error while accelerating.
    So first thing I check was the EGR, Then I changed the MAF just to be on the safe side, Then I checked the MAP sensor.
    All of the above seamed to be in good condition, The MAF I changed because I didn't know how to check.
    I went out and got myself a little generic diagnostic tool, I checked for faults and none present.
    When I go into Live Data I have some strange readings.
    My Engine is at 32-40% Load_PCT even when idle.
    The TP seams to be constantly at 4.7% whether cold, warm, idle or driving.
    The TP_R is at 4.7% and so is TAC_PCT.
    The EGR is commanded to open at idle but this could be due to the engine load been high and the ecu thinks that the car is in motion ? this is true weather hot or cold.
    My next thing to check/change is the throttle but this is getting expensive and I wanted a second opinion if this is a good idea ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
    The Baro is 99-100 apart from went I went to the next town today where it showed 97kPa.
    the map sits at 99-100 on idle and while driving I have seen it reach as high as 160kPa.
    Idle warm or cold is around the 830 rpm mark

    Do anyone have any ideas before I spend another X amount on something I don't really need.
    PS I love the car but it is getting very expensive, Acceleration feels great but I feel like it lacks torque or power when on the motorway at 110-120kph in 5th or 6th.
    Last edited by lawwolf78; 03-01-2019 at 11:51 AM.

  2. #2
    Join Date
    Feb 2019
    Location
    cyprus
    Posts
    5
    My Cars
    2008 118d se
    Morning all,
    So this morning I was playing around with the car and noted the following.
    My MAF reads around 8g/s when I block this for a few seconds (not completely) and release it the maf reads aroun d15g/s.
    The throttle is at 0% and the EGR is commanded closed. Engine load drops to 15-25% and the engine runs very smooth.
    I took the car out for a spin and it felt like another car, very different to drive.
    I put my foot down a bit and the power feels like it is in the range that it should be.
    When I came home the egr was commanded to open again and the engine load went up to 33% the throttle was at 4.7% again.

    Does this offer any help for any ideas ?
    I'm really going crazy over this.

  3. #3
    Join Date
    Feb 2019
    Location
    cyprus
    Posts
    5
    My Cars
    2008 118d se
    I have done more research today and found that the issues I am going through will be hard to pin point,
    When I block the MAF for a few seconds and then release it the Throttle goes to 0% and the EGR is commanded closed, this fixes my issue.
    If I unplug the MAF I get the same result. Tomorrow I am going to try to unplug the EGR to see if I get the same effect.
    From what I understand the throttle closes to suck less clean air in and more from the egr so the MAF readings are correct.
    If the ecu is unable to measure the air entering it closes the egr and opens the throttle.
    tomorrows test will be to see if the ecu cannot command the egr to open if it will open and allow the throttle to function.
    needless to say that with self adapting systems there seams to be no sure way to pinpoint the problem as it just moves suspicion to the next component.
    Once again everyone any help or ideas would be greatly appreciated as I am over spent already.

  4. #4
    Join Date
    Feb 2019
    Location
    cyprus
    Posts
    5
    My Cars
    2008 118d se
    Good morning all,
    So tests for today, I unplugged the EGR and took some live readings.
    The throttle was at 0% instead of the steady 4.7% although now it says at 0% regardless of driving or idle.
    Whats more I have noticed that the o2 sensor o2b1s1 for the first few mins of engine been started is at (v) 0.001 - 0.002
    after a few ins that goes up to (v) 0.212 - 0.268 but it stays in that range for the whole driving cycle.
    Now I have read that the o2 sensor should read between 0.2 and 0.8 moving up and down.
    Could my whole issue be the o2 sensor ? shouldn't a fault have come up ?
    I know you are all pretty busy but if someone could offer any help that would be great.

  5. #5
    Join Date
    Feb 2019
    Location
    cyprus
    Posts
    5
    My Cars
    2008 118d se
    well guys it is now looking like the high pressure fuel pump.
    I would like to thank everyone for not replying, even though this is a forum for helping others it seams I learnt a lot by realising I was all alone in this trial.

  6. #6
    Join Date
    Jan 2007
    Location
    .
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    Unfortunately, the 118 diesel is not available in the US. I have zero experience with that engine, and neither would any other US technicians. Glad you are headed in the right direction.
    ASE and BMW Master Certified Technician

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