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A4 1.8T Cat problems / Engine management

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by angelcakes, Oct 6, 2009.

  1. angelcakes
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    angelcakes New Member

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    [Oct 6, 2009]
    Hi,

    Sorry if this is in the wrong thread as I couldn't find anywhere to put this for a 2002 A4.

    I purchased my car a couple of months ago and driving it home the engine management light came on. It came up with a cat / lambda sensor fault so both sensors and the cat was replaced.

    The engine management light has come up again with the same fault and the garage is stumped as to why. It is also apparent that this is the 3rd cat in 7 years. The mechanic thinks that this fault may come up because the cat installed is an aftermarket cat. Has anyone heard of this throwing up an engine management fault and why the car is going through cats at a rate of 1 just over every two years?

    Also, I'm used to driving diesels and this is petrol 1.8T. I'm fairly light footed and drive about 25 miles per day up A roads and dual carriageways yet I seem to be using £20 per 120 miles. Is this normal fuel consumption?

    It passed its MOT today and I was expecting it to come up with emissions fault due to over fuelling. Thankfully it didn't but I'm stumped at the fuel usage rate.

    Any help and advice would be gratefully received.

    Thanks
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  3. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 6, 2009]
    £20 per 120miles is somewhere around 29-30mpg depending on how much your paying for fuel.

    Doesnt seem all that bad to me? Ours gets 33ish normally, but being a B5 its probably lighter, and i run the tyres at quite high pressures to save some fuel on the motorways.

    I suspect you've been a victim of the usual garage mongos who just throw parts at a problem rather than properly diagnosing and fixing it. The fact it passed the MOT means the cats working fine, and also means the lambda sensor is working fine. Without having seen the car or the exact fault codes i could hazard a guess at a faulty second lambda (the one after the cat), but thats all it is, a guess.

    Also, your car is a B6 A4, so it should probably be posted in the B6 section, but i'm sure a moderator will be able to move the thread at some point for you.
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  4. A4TSPORT
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    A4TSPORT New Member

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    [Oct 6, 2009]
    I have had this problem with the lambda sensor and the engine management light re-appearing, I took the car back and got it checkd out, I was told that the light was coming back on due to combustion and mis-firing, but the car wasnt mis-firing? however got the light switched off but told that if re-appears then bring the car back.

    Regarding the fuel situation, I feel 1.8t is quite juicy on the petrol.
    #3
  5. J7USS
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    J7USS Shuddup Foooool!!

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    [Oct 6, 2009]
    120mls to £20!!!! - - - You show Off!!:whistle2:
    #4
  6. angelcakes
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    angelcakes New Member

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    [Oct 6, 2009]
    Lol - Thanks for the replies.... Aragorn -I did have both Lambda sensors replaced and the error has been removed a number of times and keeps coming on again.....So still stumped!

    29-30 mpg is not as much as expected. Thought it was supposed to be around 33 to 35mpg.....?
    #5
  7. pjmspeedy
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    pjmspeedy Dude, what's mine say ?

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    [Oct 6, 2009]
    I get between 37-40mpg out of mine but a lot of that is motorway.
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  8. angelcakes
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    angelcakes New Member

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    [Oct 7, 2009]
    Does anyone know of aftermarlet cats bringing up the engine management lights even if the cat is working?
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  9. pjmspeedy
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    pjmspeedy Dude, what's mine say ?

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    [Oct 7, 2009]
    I haven't heard of this before but perhaps someone else maybe along later who may know of said problem.

    This is my opinion only - I can't see that someone would make an aftermarket part if it was going to cause problems. They just wouldn't bother otherwise and plus no one would buy them...... You may find you have a dodgy replacement or one of your replacement sensor is faulty!

    Just out of interest how much did the replacement Cat cost you ?
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  10. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Oct 8, 2009]
    You really need to find out the exact error code. The ECU's are quite intelligent things and will tell you exactly whats faulty, and why it thinks its faulty.

    You dont say where you are, but what i'd do is wait till it comes on again, and get a member on here to scan the car for you with vagcom and see what EXACTLY is the ECU unhappy about, otherwise you'll just keep getting hit by mongos changing parts.
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  11. zeratul
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    zeratul Member

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    [Oct 12, 2009]
    I had a very similar problem with the engine management light coming on - although it drove fine. The garage said it was a running lean fuel mixture problem along with a misfire on tickover. Short story - he changed the Lambda sensor, cleaned and swapped the plugs and injection leads, replaced some kind of head cover seal that involved new timing chains and still, the fault reoccured. Eventually took it to Audi dealer and it was just a £10 breather valve replacement.
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  12. angelcakes
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    angelcakes New Member

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    [Oct 26, 2009]
    HI, I have since had an MOT and it passed fine. Engine management light is still on and the mechanic doesn't have any idea what to do next. I'm in Norwich and dont really want to take it back to that same garage... Perhaps

    I didn't think it would be the aftermarket part causing the problem, but perhaps an issue with the car - in order to get people to bu audi parts rather than others?

    I should take it to Audi but can't afford a big bill!
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  13. angelcakes
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    angelcakes New Member

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    [Oct 26, 2009]
    The cat and two lamda sensors cost £350.... Im worried that there is an underlying problem as this is the 3rd cat and its on itd turbo.
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  14. angelcakes
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    angelcakes New Member

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    [Oct 26, 2009]
    Worth taking to Audi then as I've had the cat and sensors replaced?
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  15. no_idea
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    no_idea Member

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    [Oct 26, 2009]
    I have used Norwich Audi for some time and have found them very fair and efficient. I would go along and ask to speak to a technician and ask their advise and go from there.
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  16. Xmay4444
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    Xmay4444 On Point!!

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    [Oct 26, 2009]
    Dont know if this will help, but check your vacum hoses as well to see if any of them are split.
    Good luck
    #15
  17. idealengines
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    idealengines Enter your zip code here

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    [Jan 21, 2013]
    #16

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