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Flat Spots on Acceleration

Discussion in 'A4/S4 forum(B5 Chassis)' started by orchid66, Aug 25, 2013.

  1. orchid66
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    orchid66 New Member

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    Just a quick q for any of you who may have some understanding of my issue...

    I have a 2001 2.5TDI Q Avant with 173k on the clock that apart from a few minor issues runs very sweetly.

    However I have noticed that on occasion on hard acceleration between 3rd and 4th gear the engine dies and will not rev at all...I often have to drop back to third in order to "restore" the turbo spooling up and even miss 4th altogether in order to continue accelerating.

    This has caused more than one "close" call when overtaking and suddenly feeling like I;ve come to a dead stop when alongside the vehicle I;m trying to overtake!!

    I assume it's my MAF...have tried to put a new one on but after buying one off ebay which purported to be a direct replacement and put my car in limp mode, I am reluctant to do this until I;ve eliminated any other issues....

    advice please??
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  2. Bradderz_1988
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    Bradderz_1988 Dont replace it, Upgrade it !!

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    EGR ?? STICKY TURBO VANES ??
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  3. orchid66
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    orchid66 New Member

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    Afternoon Bradderz.....have blanked off my EGR and no difference...and if it's sticky vanes how come it only appears to be on one gear change or in one rev band area?? If I'm in 1st or second and change up at the same revs it seems fine...just seems to be mainly from 3rd to 4th (though occasionally from 4th to 5th)
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  4. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Unless its a genuine maf, its a waste of time. Cheap crap off ebay doesnt work.

    You will need a fault code scan to see what the ECU is doing.

    It could be sticking vanes as suggested, perhaps only slightly sticking at full travel or similar so sometimes it gets stuck and sometimes it doesnt.
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  5. orchid66
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    orchid66 New Member

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    Yep...found out about the cheap crap....won't be doing that again!!!

    How do I check for sticking vanes? is there a way to clean/unstick them (ie remove and strip?)
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  6. PAULF
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    PAULF Member

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    My saloon did the same - it was just at specific torque requests, normally in 4th or 5th flooring it uphill.

    Get it scanned if you can, you should find an overboost has occurred.

    Here
    is a link to a how-to for cleaning them
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  7. orchid66
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    orchid66 New Member

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    Awesome link PaulF......will try that tomorrow as the symptoms sound identical
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