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A4 AFN 110 bhp TDI running problems...

Discussion in 'A4/S4 forum(B5 Chassis)' started by Nessy, Apr 24, 2008.

  1. Nessy
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    Nessy VW + Audi mad

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    [Apr 24, 2008]
    Right, this might be a bit of a long one so let me start by explaining that I've had my A4 Avant for just over 2 1/ years, it was bought in October 05 with 115K Miles and with FSH.
    After purchase, I found that the 110 bhp didn't feel any faster than my old 90 bhp 80 TDI so I bought a cheap tuning box from Ebay Germany and it did improve the performance markedly, albeit at the expense of a fair bit of black smoke on really hard acceleration.....
    The car had a new Pierburg MAF fitted last year as I wasn't too sure about the age of the old one, and it was at a good price....lol.
    A few weeks ago I picked up a Dragon Performance tuning box second-hand (owner was selling their A4) and so removed the old 'cheap' tuning box and fitted the Dragon one.....
    It was like chalk and cheese, much more power with absolutely no smoke at all , even under hard acceleration!
    For the last few weeks I've been revelling in the increased performance as the car really is now so much more fun, and the economy if anything has become better!
    This is where my problems start really.....
    About 2 weeks ago the glowplug light started flashing intermittently and so I immediately thought that the Dragon tuning box might have been set to give too much power gain , so I adjusted the boost screw back a bit (there's an adjusting screw on the back of the unit to give more/less performance) and all was OK for a few days.........
    Alas it was not to be , a few days later the glow plug light again began winking at me again and so I removed the Dragon module off the car in case the tuning box was at fault........
    Having read of the link between dodgy brake light switches and the glow plug light flashing I replaced the brake light switch , although the old one looked OK, but at £12 it didn't break the bank.
    I ran the car (in standard 110 bhp form) for a few days and it was whilst I was joining a motorway on the slip-road that I seemed to suffer from temporary power loss, travelling at 40 mph in 4th I went to give it full throttle and the car felt as flat as a pancake, no pull at all, a change to 3rd didn't bring much increase in speed.
    It was as if there was no turbo temporarily , it was possible to accelerate through this sometimes , at other times it would stay in this slow-mode.

    I've now scanned the car with the free version of VAGCOM and it has come up with 4 engine fault codes, I'm not sure how long fault codes are stored as I've never used VAGCOM to look for fault codes on the engine before , but here they are ;

    17978 Engine start blocked by immobilser

    01268 Quantity adjuster N146- intermittent

    00553 MAF intermittent

    00539 Fuel temperature sensor G81 - Open or short to B+


    The 17978 code stumps me as I've never had the car fail to start, so I guess its been in the memory for ages......

    Having searched on here and Google for the diagnostic trouble codes 01268 and 00539 it seems these point to a sensor and switch within the injection pump , but am not sure what to do next?
    I have the old Bosch MAF I took off so think I will replace it tomorrow just to eliminate that from the equation.
    The car performed faultlessly on a 40 mile return trip to work today so it really is an intermittent issue, have checked all the cables/leads in and around the engine and all pressure hoses etc look OK.
    Short of taking it to a diesel specialist can anyone offer any advice on how to solve this problem?
    Apologies for the long post!

    Thanks

    Paul
    #1
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  3. inigoj
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    inigoj Member

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    [Apr 26, 2008]
    The quantity adjuster fault will be from one of the tuning boxes, maybe the dragon.

    The fuel temp sensor may have been from the first tuning box, if it used the older 'fuel temp' method of increasing fueling.

    The powerloss sounds like normal 'limp mode', (overboost or underboost) and is generally caused by a dirty turbo vnt mechanism, vac control leak, or N75 problem, it is a temp fault code, and cycling the ignition will restore power.

    Where did you purchase your MAF sensor, as you should only buy these parts from a VAG dealer nowadays (probably cheapest from Ford or Skoda), as the market is flooded with chinese copies that do not work well.
    #2
  4. sitrials
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    sitrials Member

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    [Apr 26, 2008]
    my A4 did exactly the same AFN engine but never through any codes only the cheap tuning box used to make the glow plug light flash, but when the box was removed it didn't and vag com never picked up a thing.
    when accelerating hard in 5th it used go into limp mode could never figure out why, and never got it fixed as it was as yours just intermittent.
    have you cleared the codes and then try again a week later?
    as for the immobilizer code could be an old code thats never been cleared!
    #3
  5. Nessy
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    Nessy VW + Audi mad

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    [Apr 26, 2008]
    Thanks for the replies gents, think I have the problem sussed.....touch wood!
    The old cheapo tuning box had an adjustment screw that if it was adjusted far enough to give too much boost etc the glow plug light would start flashing, so it was adjusted back to stop the light flashing and in that state it gave me just over 2 years of good service!
    I have cleared the codes via Vagcom and have been tinkering with settings etc over the last few days and have found if the adjustment on the Dragon box is too far advanced the glow plug light starts flashing and it throws up the DTC 01268 Quantity adjuster N146, so it has been adjusted back to a point where no DTC is generated and the glow plug light does not flash.
    I tend to agree that the immobiliser DTC code is from ages ago (think I remember setting the alarm off on the car somehow!) and the Fuel temp is a code from when the old tuning box was fitted as this code hasn't occurred since.
    The only code that kept re-occurring after clearing with Vagcom was the MAF sensor, it was a Pierburg item bought via Ebay a year or so ago and apparently the right one?
    I have re-fitted the Bosch MAF that was on the car when I bought it and so far it has not thrown up a code, so it may well be the Pierburg MAF that was at fault?
    The only other thing I've fiddled with is the valve thing that is on top of the turbo and has a cloth-covered rubber vacuum pipe pushed onto it....the very end of the rubber pipe was a bit frayed and so I removed it and cut about 5mm off the end to make it push home more securely, think I'm going to try and get some new vacuum pipe and renew the whole length of it if I can find the part number for it on Etka!
    Having now done 100 miles after re-fitting the Bosch MAF and the vacuum-pipe repair there has been no repeat of the power loss and the car goes like a rocket, so I really hope that is the end of the matter!

    Thanks again.........


    Paul
    #4

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