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1.9 tdi - poor mpg

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by subtle, May 21, 2010.

  1. subtle
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    subtle Member

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    Hey there, my tdi 130 (AVF) has had a few running issues of late so I changed the MAF meter and the problems are long gone, however the mpg seems to have dropped drasticly, struggling to reach 32mpg of late and often a quick trip to the shops will only see 25mpg or so! Likewise I just brimmed the tank and it only said 460 miles left, not the usual 600 or so.

    Anyone have any ideas, is there an ECU reset or similar that can be done?

    Any help gratefully appreciated:uhm:
    Thanks Glen.
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  2. JimLoskot
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    JimLoskot Member

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    ecu can be reset by disconnecting the battery for 10 minutes.
    don't know if that will help much but worth a try
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  3. subtle
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    subtle Member

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    Thanks for the reply, tried this yesterday, took it for a run and the mpg readout still seemed low, then the engine warning light came on! One step forward and two back.

    Will try and use a fault code reader today? Anyone else had similar issues or know of any? Any Vag tech's on here?

    Cheers Glen.
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  4. paulsb
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    paulsb Member

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    don't know if this applys to diesels aswell but i had a 325 with the same problem. as far as i know there are 3 things that control the amount fuel you use, ecu, maf and the lambda sensor. with the 325, it was a new lambda sensor that fixed the mpg.

    hope this is useful
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  5. subtle
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    subtle Member

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    Thanks for the heads up Paul.

    Got the codes read and got the info as follows: -
    Code 1
    P0234 - limit exceeded (overboost)
    calculated load - 100%
    coolant temp - 87°C
    Intake map - 252kpa
    3572rpm
    Intake air temp - 49°C
    MAF - 156.16 g/s
    Throttle position - 98.82%

    Code 2
    P0234 - limit exceeded (overboost)
    calculated load - 100%
    coolant temp - 87°C
    Intake map - 252kpa
    4119rpm
    Intake air temp - 54°C
    MAF - 161.27 g/s
    Throttle position - 83.13%

    If anyone could offer any further advice it would be greatly appreciated as this is doing my nut in and spoiling the ownership of a cracking car.
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  6. chrisash32
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    chrisash32 Member

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    Its a long shot... but lift off the gas a bit? 99%!! lol
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  7. paulsb
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    paulsb Member

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    found this site explaining fault codeshttp://www.bentleypublishers.com/tech/audi/audi.dtc.table.htm

    best guess is the boost on the turbo is too high.

    has your car had a remap?
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  8. simon.m
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    simon.m Active Member

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  9. subtle
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    subtle Member

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    Haha I wish!

    Paul/Simon I just borrowed a mates mac tools code reader, no remap I'm afraid.
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  10. paulsb
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    paulsb Member

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    best guess would be that the boost from the turbo is too high. that would explain why you mpg is lower than it should be.

    can't say for sure as it's usally petrols i play with.

    good luck
    Last edited: May 23, 2010
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  11. subtle
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    subtle Member

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    After some digging around last night I found a loose breather hose located just in front of the radiators which appears to go to a 1-way valve, reattached it, went for a spin and hey presto got 46mpg after some spirited driving and a more responsive and smoother car. So I'm a happy bunny for now lol.

    Hope this may be of some help to anyone who is suffering similar problems or the 'sticky turbo vanes' symptom.

    Glen.
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  12. iyrix
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    iyrix Member

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    Thats good! Glad you have got it sorted. I take it your just going by the DIS? Do you work your MPG out when you fill up?

    G.
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  13. subtle
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    subtle Member

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    Just used the DIS so far as we have only owned the car 3 months or so and this problem has occured for 2 months of those, but now everything is running ok I will work it all out, I'm sure there's an app for that lol.
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  14. iyrix
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    iyrix Member

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    Thats right, there is....

    [​IMG]
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