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Bounce at idle

Discussion in 'A3/S3 Forum (8L Chassis)' started by Mattfaced, Jan 29, 2010.

  1. Mattfaced
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    Mattfaced Member

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    [Jan 29, 2010]
    Hi, I have a small prob with my engine 1.8t agu. When i rev the engine and let it come back to idle it drops to about 500-600 rpm then bounces back up to 900. Any ideas anyone?
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  3. S3KO4
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    S3KO4 Member

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    [Jan 29, 2010]
    Could be your MAF, try disconecting it and have a little drive, if the problem goes away then it is likely to be the culprit. also if this didn't work you could clean the throtle body using some carb-cleaner.
    Last edited: Jan 29, 2010
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  4. ex_scoobydoo
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    ex_scoobydoo Member

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    [Jan 30, 2010]
    mine did the same, it was the MAF once i replaced it was fine, around £34 from euro parts, make sure it is a bosch, but now and again still did it, found the 1st lamba probe was gone, replaced that, seems fine now
    but the first bet is the MAF, by removing the MAF wont make no difference, it will still drop, by unplugging the MAF causes this anyway on a perfectly working car.
    best thing to do is just get a vag check on it, or try another MAF
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  5. Mattfaced
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    Mattfaced Member

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    [Feb 2, 2010]
    Thanks for your replys, Just put new plugs in and there sooty black in two weeks so i think it is overfueling. Also a slight jerk when coming on and off the power, and slight hessitation when bliping the throttle. Just had the car chiped and the power is great but these problems have developed. The car is having the manifold gasket replaced on thurs as there is a very small leak but not sure if it would cause overfueling. If this fails then getting the chip changed again.... maf was done 9 months ago, and when unpluged problem is still there. Thought maybe lambda but will try last. I will let you know the outcome. Been searching for answers on forums, checked for vac leaks found none. Need to rule out the chip before i start spending money. Ahhh i hate cars sometimes lol
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  6. Mattfaced
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    Mattfaced Member

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    [Feb 2, 2010]
    def interesing that you say the car will slill idle incorectly with MAF unpluged, will keep that in mind in future
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  7. sicupra
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    sicupra New Member

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    [Feb 2, 2010]
    Clean the throttle body.
    Your tuner should have advised that anyway. Who did it for you?
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  8. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Feb 2, 2010]
    Airleak by the sounds... check all the pipes around the inlet mani..

    <tuffty/>
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  9. ex_scoobydoo
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    ex_scoobydoo Member

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    [Feb 3, 2010]
    OVERFUELING my 1st lamba probe was dead, when i replaced it the old one was black.
    just get a diagnostic check on it mate, will save a lot of hassle.
    also clean the throttle body as sicupra said.
    #8
  10. Mattfaced
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    Mattfaced Member

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    [Feb 3, 2010]
    I have checked for leaks, but will again. Throttle has been cleaned. Strange but it only hesitates when blipping the throttle from idle, kind of coughs then revs. Almost like it over fueled for that short time, seems i am getting 40 miles give or take less from a full tank now also. I may try to pressure check the engine at the weekend, found a rather long thread about how to do it and it seems that a number of people have had success finding leaks. Unmetered air very likely but i cant as of yet find any leaks. Can anyone tell me all of the vac lines and possible places for there to be an air leak on the AGU engine. Also pcv system i pretty sure its ok as i can take the oil cap of with engine running with no problems. Sorry for the long posts wish i could get to the bottom of it. Will make sure i will post when i do as alot of threads on here seem to get left unanswered
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  11. Mattfaced
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    Mattfaced Member

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    [Feb 3, 2010]
    Vag com has no stored faults. I know you can check the lambda with a multi meter so will try that also, also think that if the plugs are black within to weeks then the lambda sure is going to be also, maybe causing more overfueling meaning blacker plugs and lambda.
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  12. Mattfaced
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    Mattfaced Member

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    [Mar 1, 2010]
    Ok so problem sorted, had the map changed and the prob went.
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