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1.8T APU Engine starting issues

Discussion in 'A4/S4 forum(B5 Chassis)' started by S4_dan, Aug 4, 2011.

  1. S4_dan
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    S4_dan Fire up the Quattro!

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    [Aug 4, 2011]
    My mate has just bought an Audi with the APU lump in it. 99% percent of the time it starts first time with no problem.

    THen occassionally, when he goes to start it, it will just crank and crank. After about 15/16 attempts, it will start but sounds like its misfiring like mad, puff of dark blue/black smoke and then after about 20seconds runs on all four fine and dandy with no smoke. And will continue like this for a days/weeks, until it decides not to start.

    He has changed the plugs, leads look new and doesnt have any other running issue once up n running.

    Nothing is coming up when i scan with VCDS (Although not tried it whilst the car struggles to start the car)

    Is this something common? Anyone else had a same/similar issue?

    Car always starts in the end, just takes alot of time sometimes before it does!

    Cheers,

    Dan
    #1
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  3. AR-rkon
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    AR-rkon Midlands regional Moderator Regional Rep

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    [Aug 4, 2011]
    Could this be an IMMO issue? if the car doesn't recognise the key, then i think it will still fuel and turn over, but not fire. thus you'd get rough running, smoke and missfire as it would be burning excess fuel that the ECU hasnt got the adequate metered air for... Just a thought.
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  4. Bradderz_1988
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    Bradderz_1988 Dont replace it, Upgrade it !!

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    [Aug 4, 2011]
    +1 with rconn more than likely be the IMMO and its still fuelling, they can be very intermittent mine hasn't done it for around 6 months and has been fine upto now touch wood lol
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  5. S4_dan
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    S4_dan Fire up the Quattro!

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    [Aug 4, 2011]
    If it was the immo, wouldn't the key light on the dash flash or something?
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  6. Bradderz_1988
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    Bradderz_1988 Dont replace it, Upgrade it !!

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    [Aug 4, 2011]
    It should in theory yes mine did, also I'd be checking it with vagcom as it should throw a intermittent fault with the key or something else I'd also check the ICM as they have a tendency to give up now and again.
    #5
  7. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Aug 4, 2011]
    immo will let the engine start then shut it down after a second or so, it will also log a fault code, and flash the immo light, so its not that!
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  8. NineNails
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    NineNails Proud sponsor of the snack food industry

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    [Aug 5, 2011]
    Does this engine have a cold start injector?
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  9. Administrators
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    Administrators Administrator Staff Member Administrator

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    [Aug 5, 2011]
    Sounds like the water temp sensor might be a little out. If the car thinks it -50degs it will over fuel on start up. Also check the ambient air temp as it will have the same effect.

    Best of luck
    #8
  10. S4_dan
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    S4_dan Fire up the Quattro!

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    [Aug 7, 2011]
    I'll do a resistance check on the water temp sensor when he comes round next.

    Ambient air temp sensor? Is that the sensor that shows up the temp on the DIS? Or is it a different sensor?
    #9

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