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rough on startup

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by dplovin, Oct 8, 2012.

  1. dplovin
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    dplovin Member

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    [Oct 8, 2012]
    i have recently bought a audi a4 1.8t

    only today has it started to idle rough on startup.

    as soon as i turn the ignition it struggles to start and then the revs drop then pick up again. or if i give it a little acceleration it starts.

    any ideas

    also it sounds like a diesel lol dam!!
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  3. Dan TheMan Welburn
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    Dan TheMan Welburn Member

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    [Oct 8, 2012]
    Best off gettin it plugged in to get a better idea of whats going on with it
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  4. pauldazzle
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    pauldazzle Active Member

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    [Oct 9, 2012]
    Common causes of rough idle on 1.8T's are. Failing coolant temp sensor, Gunked up throttle body, split vacuum/boost pipes. Scan with VCDS is useful, but may not show any fault codes relating to the aforementioned. Sounding like a deisel on cold atart up is usually caused by the Secondary air intake housing rivets failing. Noise should stop within 90 secs if it doesn't then you may have oil starvation going on, which is often caused by the Sump oil pick up being blocked with sludge.
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  5. jimmcgee
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    jimmcgee Member

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    [Oct 9, 2012]
    first thing to do is start it and see if you can remove the oil cap , if not , then pcv .
    #4
  6. dplovin
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    dplovin Member

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    [Oct 10, 2012]
    scanned it with a cheap ebay fault code reader and its came up with a fault. coolant temp sensor mate??

    could this be the cause of my issues i.e sounding like a diesel after about 5 mins plus im starting to smell oil coming from the engine and also through my vents after a short run

    last couple of days its started fine just the above now
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  7. dplovin
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    dplovin Member

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    [Oct 10, 2012]
    fault code im getting is 17698
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  8. pauldazzle
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    pauldazzle Active Member

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    [Oct 10, 2012]
    #7
  9. dplovin
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    dplovin Member

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    [Oct 10, 2012]
    Nice one buddy ill get onto it this week
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  10. pauldazzle
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    pauldazzle Active Member

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    [Oct 10, 2012]
    Just so you know. The CTS has 2 independent outputs 1 to the Dash Temp gauge & the other to the ECU. If the ECU side is sending out incorrect temp to the ECU it will not fuel correctly hence poor idle. It is quite normal for one CTS output to work normally while the other is failing.
    A lot of people decide to buy aftermarket CTS's as they are much cheaper than the genuine VAG part, problem is that rarely do the cheap CTS's work correctly for long or indeed at all. Buy cheap buy twice:banghead:.
    #9

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