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Lumpy Cold Start - Mid-High power loss.

APaulF Jan 12, 2019

  1. APaulF

    APaulF I love these cars until they break ..

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    Hey gang, my 2002 BAM with about 188xxxkms is rough and lumpy on start-up every morning or when engine is cold. Some times it's worse than others. I've scanned with VCDS and it's not throwing any fault codes. When it's warmed up it starts up and runs without skipping a beat. I've gone over all vac and boost hoses and eliminated all leaks (that I know of).

    Then whether this is related or not I don't know but it has poor Mid-High power output and bogs down then without warning it takes off with full power.

    Any help please. What do you think it could be?
    Cheers

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  3. Stuart B

    Stuart B Well-Known Member

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    are you losing any coolant?
     
  4. APaulF

    APaulF I love these cars until they break ..

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    Hi there. No I'm not. Yesterday I changed the cam cover breather hose and this morning it turned over and started perfectly. Coincidence? [​IMG]

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  5. Alex C

    Alex C Well-Known Member VCDS Map User Audi S3

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    was the old hose split?
     
  6. APaulF

    APaulF I love these cars until they break ..

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    Hey Alex, it wasn't split but it just didn't look that great, it looked very oily and worn out. I bought the car 12 months ago and it was on the car. No idea how long it's been on there though. Today, second cold start with no issues. I'll wait and see B4 I get too excited.

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  7. APaulF

    APaulF I love these cars until they break ..

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    Also it's pulling smoother through that mid to high range power but that issue is still there so I wouldn't say that's solved yet.

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  8. Stuart B

    Stuart B Well-Known Member

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    I was having MAF errors when the PCV pipe was loose as the turbo was sucking in unmetered air.
     
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  9. APaulF

    APaulF I love these cars until they break ..

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    Just thought I'd come and update on this thread. So since I last posted every cold start was perfect and didn't give me an issue at all, and for the most part that mid range acceleration has been pulling smoothly without an issue. However it does still hold back and accelerate rough occasionally but nowhere near as often as before.. (I'm still stumped)

    Anyway, I parked the car up Saturday lunchtime and I didn't drive it at all until Sunday evening and at start up it was terrible. The worst it's ever been. It eventually started but coughed and spluttered for at least 5 seconds before it did start.. The most frustrating thing is the intermittent and occasional nature of it, makes it hard to diagnose.

    Help!

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  10. fisher72

    fisher72 Member

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    I had a leak from the pipe underneath the manifold where the oil breather none return valve is and it caused lumpy tickover
     
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  11. APaulF

    APaulF I love these cars until they break ..

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    Hey mate, do you mean the crank case breather hose? I've replaced that a while ago. [​IMG][​IMG]

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  13. fisher72

    fisher72 Member

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    The green and black valve sits in the pcv pipes there was a split where it goes into the pipe
     

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  14. APaulF

    APaulF I love these cars until they break ..

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    I've deleted the PCV system so no need for that valve for me.

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  15. hendo#1

    hendo#1 Active Member

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    Failing fuel pump?
     
  16. APaulF

    APaulF I love these cars until they break ..

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    Would a failing fuel pump throw a code? I have noticed the fuel Guage doing weird **** like. One moment being 1/4 full then empty with warning light then full.. Could also be just the sender

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  17. hendo#1

    hendo#1 Active Member

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    The pump itself wont, I dont think the S3 monitors its fuel pressure either. So you wont get a code directly relating to them but it may throw other codes with regards to its running.

    I am by no means an expert on these cars though.

    The fuel pump and sender are on the same unit in the tank.
     
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  18. APaulF

    APaulF I love these cars until they break ..

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    Thanks mate.

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  19. Stuart B

    Stuart B Well-Known Member

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    It's anything else weird with your dash or only the fuel gauge.

    Have you ever replaced the fuel filter? You said if it is left for a few days it takes ages to start, maybe try it but allow the fuel pump to prime for 5 seconds before starting.
     
    Last edited: Jan 24, 2019
  20. APaulF

    APaulF I love these cars until they break ..

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    Hey Stuart, no other weirdness with the dash. I did get a fault for the fuel Guage last night (see picture) I cleared and re scanned and it's gone.

    No I haven't replaced fuel filter, I've owned it one year. And I always allow it a few seconds to prime. [​IMG]

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  21. rhubarb4

    rhubarb4 Certified Audi nutter Gold Supporter Team Silver Audi S3 quattro

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    Hi Stuart what would be the common cause of this would it be the coolant flange if he had said yes, what would your response have been, I may be loosing coolant as have residue over the passenger side of the bay, just curious what you were going to say.

    Cheers
     
  22. Stuart B

    Stuart B Well-Known Member

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    Coolant leaking on top of the pistons after pressurising the system due to a head gasket or cracked head, may be causing a slight misfire in the mornings.



    I have had a coolant flange failure S3 and a temperature sensor o ring failure TT, the coolant flange is a common failire they are only about 8 quid.
     
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  23. rhubarb4

    rhubarb4 Certified Audi nutter Gold Supporter Team Silver Audi S3 quattro

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    Cheers buddy
     

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