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audi a6 ecu problem? water in the electrics? any help out there?

Discussion in 'General Technical / How To' started by darby7, May 10, 2005.

  1. darby7
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    darby7 Member

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    [May 10, 2005]
    hi all
    i have a 2000 a6 1.8t avant. i had only driven it about 500 miles after purchasing it (i think the bloke new about the problem....)
    i started getting some idling problems. at first the idling movement was only small, it moved maybe between 900-1100 when the car was stationary. it would do this for about a minute but then it would go back to normal. this may happen twice a week. a little while after that i had a number of different light bulbs blow on me over the period of a week. just after this happened the idling problem come back but worst so i stopped driving the car.
    i left it a couple of days, went back to try it and the idling was now normal but now brake pedal was now solid! i tried to drive the car to test but to stop i had to push down the pedal with all of my force.
    i'm now really worried about my new car that i've blown all my money on!
    i left it for a couple of days to test, the brakes are now back to normal but the idling is worst than ever!!!
    i tried to investigate only to find that water has got in the passenger side and saturated the passenger foot well. i have dried it all out but the problems remains.
    i've spoken to a few people who think it may be the ecu as there is a number of problems that have occured at the same time, audi didn't really comment when i spoke to them for advise, they just want around £150 just to put it on the diagnosis machine!
    is there anyone out there that has any clue what is going on with my car?
    has anybody had a similar problem?

    any help would be really appreciated as i need to get it repaired and need to go the cheapest route using used parts if possible....? thanks
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  3. OutLore
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    OutLore VOIP Dude

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    [May 10, 2005]
    I had this exact same problem, on a 100 Avant 2.6 V6 with the exception of the brake pedal thing - and it turned out to be the alternator... basically what was happening was the regulator was pumping more than the normal voltage around the system - meaning bulbs blew and the idle and general running of the car was screwed. It would misfire for about 10 secs then clear and carry on as normal.

    Replaced the alternator and all was well.... I also changed the battery as it had been trashed by the lack of voltage regulation and would go flat after a day or so if the car wasn't started.

    Worth a punt if you can check the output on the alternator when it starts playing up.
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  4. darby7
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    darby7 Member

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    [May 10, 2005]
    thanks, i'll try that.
    i started the car earlier today, the idle went up to 3500 then back down to around 500 continuously. it has got a lot worst!
    what's the best way to check the alternator?
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  5. OutLore
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    OutLore VOIP Dude

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    [May 10, 2005]
    Hmmm... not sure mine ever got that bad to be honest, more like 1500 rpm down to idle (about 6/700) and would stop doing it after a minute or so, or if given a good thrash....

    You could check the alternator output with a multimeter, but if u r not sure I would suggest getting it into a garage. If you can get the problem to happen under a specific set of circumstances then make sure you tell the garage how to trigger it so they can run any tests while the problem is evident.

    May also be worth asking the guys in the A3/A4 forum as there are more users there with the same engine, and they may have seen something similar.... bear in mind that the engine I had is completely different to yours!!

    good luck with it tho - and if u find out what it is let us know!!
    #4
  6. ajmackie
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    ajmackie Member

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    [May 10, 2005]
    one thing ... if the idle drops to about 200rpm don't let the engine carry on running as this is around the frequency where the system becomes unstable and the amplitude of the vibrations will increase rapidly out of control and probably damage your mounts! learned that in dynamics at uni! it's ok when you start your car as your engine rapidly passed this rev frequency..
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  7. OutLore
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    OutLore VOIP Dude

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    [May 11, 2005]
    [ QUOTE ]
    one thing ... if the idle drops to about 200rpm don't let the engine carry on running as this is around the frequency where the system becomes unstable and the amplitude of the vibrations will increase rapidly out of control and probably damage your mounts! learned that in dynamics at uni! it's ok when you start your car as your engine rapidly passed this rev frequency..

    [/ QUOTE ]

    Wow. Never knew that! Cheers mate /ubbthreads/images/graemlins/smile.gif
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  8. darby7
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    darby7 Member

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    [May 11, 2005]
    me again,
    tested the alternator and it checked out to be ok. if anyone has any other thoughts on what the problem could be please post up.
    all responses are really appreciated.
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  9. audi5e
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    audi5e Member

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    [May 11, 2005]
    if it was only the idle problem, I would check the Idle Stabiliser Valve. Not too sure on the blowing of all the bulbs all at once? (that sounds more like the voltage/current spike mentioned from a faulty regulator/alternator).

    a question, is the idle rough or does it just hunt around?
    #8
  10. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [May 11, 2005]
    well the hunting,poor idle and the solid brake peddle could be attributed to a faulty/leaky servo/vacuum hose .
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  11. audi5e
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    audi5e Member

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    [May 12, 2005]
    [ QUOTE ]
    well the hunting,poor idle and the solid brake peddle could be attributed to a faulty/leaky servo/vacuum hose .

    [/ QUOTE ]

    exactly...
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  12. Jason
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    Jason Member

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    [May 15, 2005]
    Hi

    Also check if you have a pollen filter under bonnet in front of the bulk head.
    This can often be damaged or even missing which can let water in which would could seep through into your electrics.
    Also clean bulk head drain holes under plastic cover which get blocked with **** ect...

    TED
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  13. darby7
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    darby7 Member

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    [May 16, 2005]
    hi, spent some time on the weekend looking at the car. i cleaned out all of the drain channels + underneath and around the battery & the pollen filter. i'm confident that water can no longer get in the car (i left the hose on it to check) now i know that the water problem is not going to get worst i now have to try to get the problem fixed!
    on starting the car it know just cuts out when the idling goes to it's first low point. if i put my foot on the pedal i may be able to keep it running but i can have my foot to the floor and the revs go no higher than 3000 rpm, just as i take my foot of the pedal the revs go up slightly before dropping. i don't know if this has any significance?
    i now think that the vacuum problem suggested by "audi5e" (top man) is probally more likely than the ecu that was suggested before, well at least i hope anyway!!! i tried to check the hoses but could not hear any leaks over the engine noise? should the noise be clear? is there any other way to check this? even though the hard brake pedal & failing brakes has not happened for some time but the bad idling + cutting out is constant, do you still think that it is a vacuum problem?
    one thing i do not understand is that on starting the car the dash check says "OK" + all the lights go out as they should. i thought that a fault should be showing somewhere???
    any more help or advise would be great. thanks
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  14. audi5e
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    audi5e Member

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    [May 17, 2005]
    that check light on the A6 does not check everything, only critical items like water temp, oil pressure, worn brakes or a fault in the brake system.

    one way to check for a vacuum leak is get a length of rubber pipe, then holding one end to your ear, run the other end across all the vacuum hoses/pipes/inlet manifold (hold it close) it is much easier to isolate a problem. Sometimes the leak is obvious and you can see a tear in a hose or hear a loud sucking noise, other times you have to do some searching.

    try taking the brake vacuum hose off the engine and plugging the pipe on the engine, then try plugging each vacuum hose in turn trying to isolate a leak.

    Check that all the engine breather hoses are connected properly as vacuum will be lost here too.
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  15. foolish3uk
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    [May 19, 2005]
    sounds like you have a leak in the vacuum pie causing the rough idle as said above this will also cause brake problems as it gets the vacuum off of the manifold. audi's are common to the throttle valves getting carbon dirt build up, recommend undoing the throttle boost pipe near the throttle valve and cleaning the inside where the butterfly sits this will give you a much steadier idle, the vac pipes sometimes crush at the bulk head area (worth having a look).

    the pollen filter housings are quite common but more so are the drain plugs in the bottom of the plenum chamber x 2 and the air con drain which is situated in the passengers foot well!

    good luck
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  16. darby7
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    darby7 Member

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    [May 20, 2005]
    thanks for all your responses guys, i'll try and have another look this weekend.
    in response to petetdi i'm down in Croydon, South London. i'm very close to Croydon Audi but they want silly money to put it on a fault diagnosis machine. one problem i have is if the car is driven it stalls all the time due to the terrible idling + i can never be sure if the brake failure will return!!!
    if you know any one in my area that could help please let me know. cheers
    #15
  17. darby7
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    darby7 Member

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    [Jul 19, 2005]
    oh dear!!!
    after a mission getting vag-com to work on the laptop i eventually was able to scan.
    here are the faults..........

    17544 FUEL SYTEM TOO RICH
    17536 FUEL SYSTEM TOO LEAN
    16684 RANDOM MULTIPLE SYSTEM MISSFIRE
    16685 CYLINDER 1 MISSFIRE
    16687 CYLINDER 3 MISSFIRE
    16688 CYLINDER 4 MISSFIRE
    16686 CYLINDER 2 MISSFIRE
    17925 MAIN RELAY (J271) ELECTRICAL MALFUNCTION

    these are the main bits, the others were minor bits a/c, alarm etc.....
    there was a part number mentioned.... 4b0 906 018 bf component 1.8l r4/5bt g 006. i do not know if this helps.

    any advise to what to do next?
    i guess the main relay needs replacing asap (what one is the main one? is it with the other relays?) but any advise as to where to start or what parts to look out for would be really appreciated.

    is it possible it still could be the suspected brake hose leaking or do these fault codes suggest something else????
    thanks
    #16
  18. audi5e
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    audi5e Member

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    [Jul 20, 2005]
    Not sure on that part number, you will have to ask Audi.

    Personally I still think there is a vacuum leak somewhere. Especially will all those missfire reports.

    But, try changing that relay first and see if that makes a difference?
    #17

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