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Thread: MAF sensor

  1. #1
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    Question MAF sensor

    Been reading up on Maf sensors and wondered if mine was faulty (fuel consumption heavy) I unplugged sensor and had a good drive about, engine running ok, no spluttering etc. if anything it seemed more responsive,the only difference was a warning light on the dash. Went into my local dealer in Carlisle to enquire and they told me that it was a MAP sensor not a MAF and that by unplugging it from the air intake would only record a fault on the engine mamagement system, they advised me to get a diagnostic check from themselves which would take approx. 1 hr at a cost of 90.00. Has anyone else had this problem, would be grateful for any advice.

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    evilscotsman's Avatar
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    The sensor at the actual airbox, immediately after the filter, is definately a MAF (Mass Air Flow) sensor. The MAP (Manifold Absolute Pressure) sensor is attached the the intercooler hidden under the passenger side wing so-to-speak, so if they said the one at the airbox is a MAP, and thats the one you unplugged, then they are talking complete ******. Keep your 90, and put it towards a MAF, because you rightly diagnosed that it runs perfectly, better even, with it unplugged then that shows it is giving incorrect info to the ECU and is faulty.

    You can try spraying it with carb cleaner (not while running!!!) and its easy to remove to do it right.

    Take it off, you'll see a sort of cross-hair gun sight bit - thats the sensing element, its a Hot-Wire Anemometer type, that measures the cooling effect of the air passing over it, so when it gets gunged up at all from filter oil, or any contaminant, because its hot then **** "cooks" onto it, so that it then gets coated with a yucky film it cant cool so incorrectly tells the ECU the airflow is WAY lower than it really is, resulting in weak fuelling.

    Try cleaning it - NO CONTACT with the element tho, just spray it until all the crud is removed and its sparkling inside, then try that, if that doesnt help (and it will most times) then the element is fooked and just buy a new one from www.vagparts.co.uk - if as you say your consumption is heavy, perhaps yours is busted, and the ECU thinks the airflow is much higher than it is, so cleaning may not help your problem.

    Search for MAF or put your MAF part number in....heres the one for example that fits certain engine codes (not mine for instanceas mines a BFB engine)

    https://sslrelay.com/s74326199.onean...06A906461AV=29

    (its still vagparts just thats the url they use to load the page)

    Its about 90, replacing a faulty one will put the DTC light off and the car will be fine, if its still running badly then you can get a refund and get a diagnostic then, but your likely right about it. Remember try cleaning first, its an OLD problem dating from MK3 golfs onward.

    Last edited by evilscotsman; 19th September 2008 at 09:12.
    B4 TDI - old skool project / daily driver...if it ain't broke, it's probably an Audi...


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    Thanks again Scotsman, have reconnected sensor today, now engine management indicator showing on dash,will this cancel itself or do I have another problem?

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    evilscotsman's Avatar
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    I havent had a faulty MAF yet (thankfully touch wood) but ive seen a lot of posts on veedub, audizine and others re maf failure. I would say that any DTC fault code that occurs will give a CEL but others have said that fitting a new maf put the light back out as the computer realises the maf is now working, and just stores the code.

    You might need to simply disconnect the battery for 10 mins and do the usual like set the clock etc afterwards but although the ecu will have stored the code it should start from scratch, first doing a TBA (throttle body alignment) - lots of whirring and clicking, when thats stopped (ign on after reconnecting battery, dont start engine just ign on) the engine will be ready to start and hopefully since all is well the CEL should not come on.

    At worst, see if someone local has vag com or a hand-held OBD device that can reset the CEL and if it just comes back on, the fault is solid.

    Did you mean you connected the original maf back up or a new one? If its the original and the light only appeared after disconnecting it, then the ecu mustnt have realised it was faulty, and only noticed when you pulled the plug, a reset should clear it no problem, but has you original fault returned after putting the maf back on or has it now gone away? Might have been a bad/dirty connection now made good, or if youve cleaned it, and its working fine, the CEL will be a dummy from the time it was removed so reset & your good to go!
    B4 TDI - old skool project / daily driver...if it ain't broke, it's probably an Audi...


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    With the original MAF sensor disconnected the ECS and ESP indicaters show on dash, when MAF reconnected ESP clears immediately after starting but ECS takes some time to clear, any idea why the ESP should show a fault ?

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    evilscotsman's Avatar
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    I dont know mate, thats strange. The ESP light should only be visible when the traction control is off.

    Unless some strange fault afflicts the electronics of the ECU....
    B4 TDI - old skool project / daily driver...if it ain't broke, it's probably an Audi...


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    Had diagnostics checked today at dealers, luckily done under warranty, they replaced MAF sensor but now car running worse than before, seems very slow to pick up. Had a good drive about and noticed that unlike before I can not hear the turbo ( it used to whine as it kicked in ).
    I have contacted the dealers who have asked me to return the car tomorrow, do you think they might have fitted a faulty MAF ?

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    Problem sorted, turned out to be disconnected wire caused when fitting new MAF sensor.

  10. #9
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    glad you got it fixed matey!
    B4 TDI - old skool project / daily driver...if it ain't broke, it's probably an Audi...


 

 

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