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Checking for a faulty MAF

Discussion in 'A3/S3 Forum (8L Chassis)' started by doublem_1, Oct 29, 2011.

  1. doublem_1
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    doublem_1 Member

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    I'm sure I have a boost leak which I will be looking into in a few days time. However, just to rule out the MAF, I would like to try running the car with it unplugged. Now, my question is, will this through up a check engine light on the dash? Its a 1.9TDI.
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  2. Paradox1
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    Paradox1 Active Member

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    I think your eml will come on.a faulty maf is usually found when driving and the throttle. surges and pulls back. you can try cleaning it with some contact cleaner. if not its a replacemwnt. you should get the boost leak sorted first as it may not be the maf
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  3. doublem_1
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    doublem_1 Member

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    Ok, I'll sort the boost leak out first. It's just that because at the moment its cold in the morning the engine hardly boosts at all until it warms up after a few minutes. I have read that it could be a faulty MAF.

    I don't really want the eml on tbh.
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  4. macpdm
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    macpdm Member

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    Dont worry the EML will go off after a short while once the MAF has been plugged back in.Ive done it to mine a number of times without problems.I believe you can unhook the positive lead from the battery for a short while to clear any codes but you may need the radio code.Try checking & cleaning/replacing your DV and clean the throttle body.Ive been suffering with similar problems to you and doing this seems to have solved it.
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  5. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Have you had the fault codes checked with VCDS yet? have said this on more than one occasion but anyone trying to diagnose a fault should check codes in VCDS first else you are going in blind...

    <tuffty/>
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  6. doublem_1
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    doublem_1 Member

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    I had it scanned a few months back and the only code was reporting a misfire on cylinder 3. I have bought a new injector loom which I hope will help things.
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  7. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    What makes you think your MAF is faulty? is this due to the boost leak?

    Ideally you need to log airflow and see if its anywhere close to whats its supposed to be... while that won't rule out a faulty MAF it should give you a start point...

    I have seen MAF sensors under read before now so to all intent and purpose the ECU thinks all is ok...

    Isn't a common prob on TDi's the variable vanes of the turbo getting clogged? think this leads to lack of boost assuming this is the problem you are having...

    <tuffty/>
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  8. doublem_1
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    doublem_1 Member

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    Yes I am also thinking the vanes are sticking. I shall be buying some innotec cleaner as I have read this usually sorts it out.
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  9. jojo
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    jojo S3 Drift King! Staff Member Moderator

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    If the vanes are sticking, a quick blast in 3rd gear at full throttle sometime clears it up!
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