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Thread: Td5 Engine Surging

  1. #1
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    Td5 Engine Surging

    2004 D2a auto.


    My D2a engine has little, intermittent surges - revs go up by about 100-200 RPM for very short periods. Nothing major but I can feel the surges whilst driving - mostly around 70 - 80 kmh but also when sitting at traffic lights idling.


    I have switched off cruise control but that made no difference.


    When I next have the time I'll check the ECU plug although I've never had any oil in the external loom yet.


    Not sure if relevant but I have just replaced the whole FPR assembly.


    Anybody had similar symptoms or any ideas of where to look?


    Hopefully, I can get to the bottom of this quickly as I'm off to central Australia in a few weeks!


    Cheers,


    Franz

  2. #2
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    Er , air conditioning wouldn't be on by any chance?
    Unless you have pressed "econ" the compressor is working .
    Regards Philip A

  3. #3
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    Quote Originally Posted by PhilipA View Post
    Er , air conditioning wouldn't be on by any chance?
    Unless you have pressed "econ" the compressor is working .
    Regards Philip A
    Hi Philip A,


    No, not the AC - unusually, I was running all day without the HVAC system.

  4. #4
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    Hi, do you have EGR?
    if you dont have access to diagnostics to read some live data
    1. unplug the MAF and see if it cures it or not, a bad MAF would cause that on a auto
    2. clean the AAP sensor(the one in the airbox) with electronic contact cleaner spray
    3. inspect the upper plug too which connects to the injector loom, if it's oil there the injector loom is already gone you dont have to expect the oil to get to the ECM
    do you have EGR?

    the best would be to plug in a tester though otherwise it's a guessing game
    Discovery Td5 (2000), manual, tuned

  5. #5
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    Quote Originally Posted by sierrafery View Post
    Hi, do you have EGR?
    if you dont have access to diagnostics to read some live data
    1. unplug the MAF and see if it cures it or not, a bad MAF would cause that on a auto
    2. clean the AAP sensor(the one in the airbox) with electronic contact cleaner spray
    3. inspect the upper plug too which connects to the injector loom, if it's oil there the injector loom is already gone you dont have to expect the oil to get to the ECM
    do you have EGR?

    the best would be to plug in a tester though otherwise it's a guessing game
    Hi Sierafery,


    EGR is disconnected.


    I do have a Nanocom and took some fuelling input recordings yesterday but, I'm not sure what to look for in the data or, do I need to record some other data?


    I'll have a look at the other items on your list this morning.


    Thanks for the suggestions.


    Franz

  6. #6
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    record live data(instrument mode) on a longer drive then convert it in excell file and post them here....didnt you get any fault codes logged?

    if you can't do that watch ambient pressure on instrument mode and see how it behaves when the symptom occures... air flow as well
    Discovery Td5 (2000), manual, tuned

  7. #7
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    Quote Originally Posted by sierrafery View Post
    record live data(instrument mode) on a longer drive then convert it in excell file and post them here....didnt you get any fault codes logged?

    if you can't do that watch ambient pressure on instrument mode and see how it behaves when the symptom occures... air flow as well
    How do I convert the Nanocom data into Excel format - can't seem to find any info on how to do it with a Gen1 Nanocom - user manual was not revealing either.


    This morning I checked the ECU plug at the rocker cover - no oil to be seen.


    The symptoms are intermittent - this morning she ran fine but started to play up in the afternoon.

  8. #8
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    it saves as a csv onto the card

    Save the file to your computer

    Open it with excel (right click open with)

    select the column - then Data>Text to columns

    It will then create columns from whatever the csv file has used to separate the data.

  9. #9
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    Quote Originally Posted by stallie View Post
    it saves as a csv onto the card

    Save the file to your computer

    Open it with excel (right click open with)

    select the column - then Data>Text to columns

    It will then create columns from whatever the csv file has used to separate the data.
    Thanks Stallie but in my case it does not save it as a *.csv file - it's an *.ful file and when opened in Excel shows a whole bunch of gobbledygook!

  10. #10
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    OK, so today I cleaned the MAF and the AAP sensor. I then also bridged the boost modulator and took the car for a spin.


    I did not feel any surging but the engine is still a little lumpy. I guess this is still not conclusive as she ran fine for half a day yesterday and then started to play up.


    So when I got home I did some more research on faulty MAF sensors. I found this information on the AULRO


    Resistivity values taken from MAF sensors
    New OEM MAF:
    Pins 1-2 = 16.8 kohm
    Pins 1-3 = ~34 Mohm
    Pins 2-3 = ~34 Mohm


    I then measured my MAF and got the following:


    Pins 1-2 = 16.8 kohm
    Pins 1-3 = 16.38 Mohm
    Pins 2-3 = 16.34 Mohm


    So, I guess that I will need to replace my MAF?


    So, I have unbridged the boost modulator and disconnected the MAF and will take it for a drive over the weekend and see how it goes.


    Cheers,


    Franz

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