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Thread: VW T4 2.5 AET cutting out

  1. #1
    Join Date
    Jun 2011
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    Vic
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    VW T4 2.5 AET cutting out

    For some reason my T4 2.5 petrol has developed an intermittent fault - when driving in the first five minutes from startup it will occasionally and without warning drop power. If I'm going at a little speed you feel this by the sudden jerk of deceleration, which can be quite violent and shove you into the belts at worst. The engine keeps running after the jerk - it might happen 2-3 times and then the rest of the journey is fine. It happens regardless of throttle angle. At othertimes I have had the clutch in when it happens and the engine dies - easy to restart, most of the time. It happens when the car is running on lpg or on petrol. It happens even if the car is warm from the previous run.
    Any ideas what this might be: coil fault?

  2. #2
    Join Date
    Aug 2016
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    NSW
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    Most likely.
    They are cheap enough to try first up.........and fairly easy to access!
    Although, I seem to remember changing the coil needlessly once and it turned out to be the disi cap or the lead.
    2018 Crafter Runner
    T5.1 6sp manual.

  3. #3
    Join Date
    Oct 2008
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    There is also the engine controlrelay to consider , I can,t remember what number it is but it did similar things to mine as you describe , for some reason you would be driving along the engine would cut out and if in gear restart almost immediatly . Then sometimes without warning around town it would cut out at the worst places , one afternoon in peak hour traffic it cut out and wouldn,t start . So as I was on the inside lane I just left it in gear and used the starter to slowly creep it onto the footpath , few minutes later it would start again .

  4. #4
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    Thread Starter
    Quote Originally Posted by Sunny43.5 View Post
    There is also the engine controlrelay to consider , I can,t remember what number it is but it did similar things to mine as you describe , for some reason you would be driving along the engine would cut out and if in gear restart almost immediatly . Then sometimes without warning around town it would cut out at the worst places , one afternoon in peak hour traffic it cut out and wouldn,t start . So as I was on the inside lane I just left it in gear and used the starter to slowly creep it onto the footpath , few minutes later it would start again .
    That sounds like the problem - what No relay?

  5. #5
    Join Date
    Oct 2006
    Location
    Perth WA
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    103
    Relay 30, cream colour.
    Pt no is 165 906 381

    Slightly hidden by the metal bracket in front of the fuse box.

    $40.70 for a genuine one from the VW dealer.
    2.0L 16v Audi 80 - Project
    3.0L 30v Audi A6 quattro - Daily

  6. #6
    Join Date
    May 2006
    Location
    Adelaide South Australia
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    1,298
    I don't own the petrol T4 but on the TDIs it's common for the ignition switch to wear out. Just a thought.
    Understand how it works, troubleshoot logically BEFORE replacing parts.
    2001 T4 TRAKKA Syncro 2.5TDI,2006 Mk5 2.0TDI Golf manual,2001 Polo 1.4 16V manual [now sold], '09 2.0CR TDI Tiguan manual,
    Numerous Mk1 Golf diesels

  7. #7
    Join Date
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    Quote Originally Posted by 16v80 View Post
    Relay 30, cream colour.
    Pt no is 165 906 381

    Slightly hidden by the metal bracket in front of the fuse box.

    $40.70 for a genuine one from the VW dealer.
    Thanks 16 V I figured someone would remember the number of the relay , bugger of a thing as the dealers could not diagnose the fault in the relay unless it cuts out while connected to the diagnostic gadget . After the time it stopped on the side of the road I became paranoid about it cutting out in the middle of an intersection , I was at the dealers service dept and begged them to see what was wrong, suddenly a voice from the parts department over heard us and yelled out try the relay . He had one in stock and voila never did it again , I could have kissed him { not in that manner } I,m straight ha ha

  8. #8
    Join Date
    Aug 2016
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    NSW
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    Oh, yeah.......I forgot about that relay.
    (You ever see those Queenslanders at State of Origin time huggin' and kissin'?
    Yeah....I wonder about them too...........)
    2018 Crafter Runner
    T5.1 6sp manual.

  9. #9
    Join Date
    Jun 2011
    Location
    Vic
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    171
    Thread Starter

    OK, I have the solution to this:
    Replaced the coil with the spare = no change.
    Replaced relay 30 = no change
    Scratched head, blew coolant hose under exhaust and got towed to Dandy Volks and paid for major service.
    Problem was plug leads!
    I had put new KYB plug leads and Bosch plugs in some 10,000 km ago and the match was not a ood one. The inside of the plug leads and the top of the plugs showed evidence of erosion from arcing.
    Now the car runs very much better, can accelerate from 100 to 125 with ease and I expect some improvement with economy.
    So ... check the basics first.
    I've replace the crank angle sensor and the distributor, the latter I had bought for $30 off've ebay to get the rotor and cap, so I thought I may as well use it.

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