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Hesitation/misfire and rough running. Help appreciated

Discussion in 'A3/S3 Forum (8L Chassis)' started by Curt, Jun 28, 2013.

  1. Curt
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    Curt Member

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    [Jun 28, 2013]
    Hi all,

    I've got an issue with my Revo stage 1 1.8T.

    Well when I got my car back I noticed that there was a "jerk" as you let of the accelerator but stayed on the throttle slightly, nothing wrong if you let off completely. It was definitely an engine running related problem, not a mount or anything.

    This was annoying but not the end of the world whilst I tried to diagnose it. Unfortunately, it just got worse. I pulled away from a roundabout and it hesitated massively until I let off, then did it again. Then it would clear for a bit, then do it again. When it did pull fairly normally it still wasn't right. I pulled into a petrol station and unplugged the MAF to see what the difference was. It made it a lot worse. It got better as I got near home, but still not normal. The only other weird thing is it dropped to 20 miles left just before home, but no warning or beep to tell me?

    Anything obvious I can check/replace tomorrow? I've got to be in Poole and really don't want to like this.

    The only thing I changed recently is putting the S2k filter on yesterday but I can't see that affecting it and it was fine on the test drive.

    I should point out it is running on high octane, and has a Forge splitter fitted. I know these are a no no, but it was on the car for around 2 years the last time I owned it with no ill effects. It's set to recirculate.

    Any help would be appreciated.

    Cheers,
    Curt
    #1
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  3. Tim_Attard
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    Tim_Attard Active Member

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    [Jun 28, 2013]
    be prepared for the forge splitter comments :p however i doubt this is the issue it sounds a bit like my car tbh at the moment and ben thinks its a vac leak so id get that checked first apart from that im not much help
    #2
  4. Curt
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    Curt Member

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    [Jun 28, 2013]
    I've seen lots of negative comments about it... I will get it changed as soon as I can afford to but as I say, it was fine for a long time. I'm going to go get some bits tomorrow, clean the throttle body and all connectors, check for leaks, possibly plugs and fuel filter. It's very annoying!
    #3
  5. Tim_Attard
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    Tim_Attard Active Member

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    [Jun 28, 2013]
    little tip theres alot of people like us (before joining asn) on ebay that pay quite a bit of them £80+
    #4
  6. Curt
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    Curt Member

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    [Jun 28, 2013]
    Yeah I know, cheers. That's where mine came from but I didn't pay that... It'll go on there when I get a standard or 007P
    #5
  7. jezzy
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    jezzy Member

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    [Jun 28, 2013]
    If you have ESP turn it off
    #6
  8. Curt
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    Curt Member

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    [Jun 28, 2013]
    No I don't, it's too old and it wouldn't be on
    #7
  9. jezzy
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    jezzy Member

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    [Jun 28, 2013]
    ok one to cross off.
    Do you have old coil packs too?
    #8
  10. Curt
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    Curt Member

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    [Jun 28, 2013]
    Coil packs have never been changed as far as I'm aware, but as I have an AGU I've heard they very rarely fail and it's usually the ignition control module thing. But it doesn't seem to misfire at all and it's not dropping a cylinder at any point
    #9
  11. jezzy
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    jezzy Member

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    [Jun 28, 2013]
    Could be just your wiring from the coil packs, they sometimes break down due to heat.(especially after a remap)
    And its free to check and fix
    #10
  12. Curt
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    Curt Member

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    [Jun 30, 2013]
    I've checked the wiring to the coil packs and all seems fine. The remap was done around 3 years ago and this is the first issue I've had...

    A little update on this... Before leaving yesterday I changed the spark plugs, fuel filter, oil and filter, cleaned the throttle body, cleaned the MAF and cleaned/checked all wiring/plugs I could see as related to the ignition system.

    The good news... It pulls much better and for the most part runs and feels great. BUT, it is still hesitating very slightly, and the jerk when you let off the throttle is still exactly the same.

    It feels very sensor-ish to me... anything likely? Coolant temperature sensor? I know I need to get it on diagnosis really :(
    #11
  13. Mikey3000
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    Mikey3000 New Member

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    [Jun 30, 2013]
    I have exactly the same problem mate. I have had the thermostat and coolant temperature sensor changed - both were faulty in their own right. I have also very recently had a major service at my local specialist (done to Audi spec). The maf has been changed halfway through the life of the car and I have also had the throttle body striped and cleaned.

    The symptoms I experience is that the car idles around 1200 when firing up from cold. After three minutes ish this drops to 1000 and then after another five or so minutes it drops to just under 800. My idle flutters ever so slightly but this improves as the engine warms and the idle speed drops. I also find that when I first start the car and drive off, the engine hesitates under light to moderate acceleration. My money is on a vac leak and I think it is definitely a good idea for you to explore this area as well.

    My theory is that as the engine warms, hoses will expand with temp increase which will help to close up any splits, thus reducing the affect of symptoms as the engine warms.

    Let me know how you get on with yours mate as we may be able to help each other sort this annoying problem.

    Mike
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