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Car revving itself on idle ?

Discussion in 'A3/S3/Sportback (8P Chassis)' started by A3Craig, Sep 23, 2013.

  1. A3Craig

    A3Craig Member

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    Hi All

    Had the problem the other day I drove home from work and when I pulled onto my drive I let it idle a few mins like normal and the revs increased and went back down so I thought I might of twisted the mat or pressed the accelerator so moved mat out the way and it did it again and went upto 1500rpm and continued fluxuating.

    Next day was fine until again I got home, so it only seems to do it when its warm, also have noticed my mpg has gone down, done a search on here and it points to a breather problem so I have checked the PCV valve and that seems fine, I have also tried removing the oil cap when the problem occurs and it is very difficult as its under a vacuum.

    Where do I start looking or common failures ?

    Thanks in advance
     
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  3. S3_Mat

    S3_Mat Active Member

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    MAF?
     
  4. Brodster

    Brodster Well-Known Member
    Team Ibis VCDS Map User Audi Avant Owner Group Audi S4

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    Mates car had this. Turned out to be the fuel flow valve.
     
  5. Granta

    Granta Active Member

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    Is it a petrol or diesel?
     
  6. A3Craig

    A3Craig Member

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    Don't think its MAF as this wouldn't cause a vacuum,

    Thanks- will look into fuel flow valve

    The car is a 2006 Audi A3 2.0t petrol 200bhp

    thanks for responses
     
  7. A3Craig

    A3Craig Member

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    Just been doing some googling and Broadsters solution has come up a few time with all the same symptoms and part is very cheap and easy to fit which I do like lol.
    going to get one order and fitted and go from there
    Thanks again
     
  8. S.

    S. Well-Known Member
    Team Ibis Audi S3

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    do you have the part number and price that you would like to share, so it's handy if i have to replace it or anybody else :icon_thumright:
     
  9. A3Craig

    A3Craig Member

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    Im away this week on a course but am back Friday so will get one sorted then hopefully and will post part no up and price :thumbsup:
     
    S. likes this.
  10. phil76

    phil76 Active Member

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    Cant the pcv also cause this ?
     
  11. A3Craig

    A3Craig Member

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    Have taken pcv off and one way valve is fine

    thanks craig
     
  12. A3Craig

    A3Craig Member

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    Got back and have got the n80 valve, part no is 06E 906 517A

    took 15mins to fit and was easy as it gets

    time will tell if it has worked and I will update in a few days
     
  13. A3Craig

    A3Craig Member

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    The n80 valve has made a difference however the fault is still there and now has brought the engine management light in saying. System to lean bank 1

    any ideas as getting stuck now

    thanks Craig
     
  14. A3Craig

    A3Craig Member

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    Bump
     
  15. RobinA3

    RobinA3 Well-Known Member

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  16. A3Craig

    A3Craig Member

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    On the boost pipes, As thought in was vacuum related?

    not saying your wrong lol just confirming I I can check the right bits :)

    Thanks Craig
     
  17. RobinA3

    RobinA3 Well-Known Member

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    It could be you boost pipes - basically you need to check all the pipes from the maf sensor to the throttle body - the way the diagnostics system works is by measuring the airflow going through the maf sensor and comparing that value to a calculated value flowing through the throttle body, now if there is a difference in airflow between the 2 then it will throw up a fault code.

    During idle or part load running the system will be in vacuum so it will be drawing in air after the maf sensor meaning that the engine is still getting the same amount of air however the maf hasn't measured some
    of this air.

    I have seen this issue many times during my 8yr career in engine development on Bosch ecus.
     
  18. A3Craig

    A3Craig Member

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    Thanks for your response, I will have a look and report back
    thanks Craig
     
  19. A3Craig

    A3Craig Member

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    Just jacked the car up and the two boost pipes connecting to the intercooler were both not connected very well so have cleaned them up and reconnected and reset engine light so wait and see what happens tomorrow
     
  20. A3Craig

    A3Craig Member

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    You may be right with this being the problem, I disconnected the maf and the car no longer goes crazy on idle, it does still rev a tiny bit and also the revs are slower to return to idle but assuming this is because the car does not how much air is going into the engine?

    So guessing replace the maf?

    thanks craig
     
  21. Mujnu

    Mujnu Active Member

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    Sorry to dig up an old thread, but I've been scouring this forum and a lot of others but no one seems to have the same probem as me lol :/

    My car is a 55 (06) plate A3 1.9tdi, BKC engine code with 120k on the clock.

    I've realised when my car is idle my revs will rise from approx 850-900 rpm and sit on 1000rmp (just a little above). This can be from a cold start, when i start the car first thing in morning the revs will rise and as the engine warms up it'll auto-rev to 1000rpm every time i sit at idle. When the revs do rise if i press the accelerator it'll drop back to 850rmp only to rise a few seconds later.
    Ive also realised every time the car revs the fans kick in for about 30-45 seconds and then stop but the revs will stay at 1000rpm. I have checked battery voltage and its not a bad battery causing it.

    Theres no codes apart from glow plugs which i don't think should effect the rpm, so not sure what it is, any help would be much appreciated lads. Thanks
     
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  23. Mujnu

    Mujnu Active Member

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    Got this sorted a few months back but forgot to update. Mine turned out to be the alternator belt and pulley. All sorted now.
     

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