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Really really bad MPG problem!!

Discussion in 'A3/S3 Forum (8L Chassis)' started by DJ_Troopa, Jan 9, 2012.

  1. DJ_Troopa
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    DJ_Troopa K1 Driver

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    About 5 days ago my car MPG decided to drop drastically! I do alot of local driving as i work about 5-6 miles away, but my MPG has been 24-25. Then 5 days ago it decided to drop to 21 and i hadn't even booted the car! Within a few hours it went down to 18 and even when i was stuck in traffic it decreased to 16.3!!

    When the engine is running and i'm not moving, you can see the MPG dropping every 20-30 seconds. WTF has happened!?

    - Done a pressure test last night via the DIY tennis ball method and came up with no leaks
    - MAF is few months old
    - Lambda on downpipe is few months old
    - Service done just before summer inc. fuel filter changed
    - Liquid gauge brings up no fault codes

    Any idea's? This car is seriously pissing me off now :(

    Thanks

    Ajay
    #1
  2. Westy
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    Westy Double Dark Side! Diesel & 8P

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    Have you checked the vac hose to the FPR to ensure it has no splits?

    Also is your thermostat and temp sender ok? If the car thinks it's running cold it'll be over fuelling as it'll be on it's warm up cycle.
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  3. DJ_Troopa
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    DJ_Troopa K1 Driver

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    I have no temp issues with the car, it reaches 90 and stays there so it can't be that either. CTS was changed in summer too!
    #3
  4. Westy
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    Westy Double Dark Side! Diesel & 8P

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    Ok, what about the FPR hose? Tell me it's not the original manky hose.
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  5. DJ_Troopa
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    DJ_Troopa K1 Driver

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    lol nope it's not mate, i got a black silicone vacuum pipe on that and also on the dv too.
    #5
  6. Westy
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    Westy Double Dark Side! Diesel & 8P

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    Hmmm, and you're noticing the drop in mpg from idle and easy driving rather then driving it like you stole it?

    Might be worth popping the FPR and injectors and giving them a clean.
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  7. Alex C
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    Alex C Well-Known Member

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    has somebody recently reset the average MPG on the DIS? In which case your ave MPG will fluctuate quite regularly to start with. And when sitting in traffic your ave MPG will drop, your burning fuel on idle but your not going anywhere so your actually doing 0 mpg which will pull you ave. MPG down

    have you noticed any difference when you drive other than the DIS reading? like power?
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  8. DJ_Troopa
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    DJ_Troopa K1 Driver

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    I've reset the DIS on several journeys now but it keeps dropping down. I've noticed a slight power difference yes, car feels alot smoother than before and doesn't have that much poke as it used to.
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  9. Westy
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    Westy Double Dark Side! Diesel & 8P

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    Think you need to get it on the rollers for some diags mate.
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  10. DJ_Troopa
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    DJ_Troopa K1 Driver

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    I think so too :( If i can hold out for another week or so i'll organise to go see Bill and have it checked out. This car is doing my nut in, just want it running fine for once and then it's for sale next year!
    #10
  11. Westy
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    Westy Double Dark Side! Diesel & 8P

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    For Sale!!!! Why?

    Bill will tell you what's wrong with it.
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  12. DJ_Troopa
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    DJ_Troopa K1 Driver

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    Time to move on and actually start saving again. This car has drained so much out of me and i can't do it much longer! Whoever gets it next will be lucky as everything would have been changed and will be stage 2 ready! I'm 25 next year too so that opens alot of options for other cars :)
    #12
  13. Westy
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    Westy Double Dark Side! Diesel & 8P

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    You'll miss it mate, especially when it's running right.
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  14. DJ_Troopa
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    DJ_Troopa K1 Driver

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    Yeah i know what you mean. But every 2-3 months something has gone like a sensor or some **** lol. I think i've got the car at it's time where things need changing which is unfortunate for me but what can i do eh!? Just gotta keep on top of it!
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  15. Westy
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    Westy Double Dark Side! Diesel & 8P

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    I got on top of my issues and am now upping the power and enjoying the car. It's fun now.
    #15
  16. sportstractor
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    sportstractor Chugger

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    i never take notice of the DIS, they are so bad on the 1.8ts. i once did a 300 miles motorway trek and managed 36mpg according to the dis, then when i came off the mway, and went up the first big hill (3 miles long), i smashed it up there, then it dropped from 36 to 30 mpg... how on earth can that be possibly lose 6mpg on a 300 mile journey on a strech of road only 3 miles long... i would of have to use 7.5 ltrs of fuel to make it drop that much... simply not possibly. Just saying take the DIS with a pinch of salt.

    have you tried logging any WOT runs, motoring fuel trims and lambda. I put up quite a useful link on this thread the other day http://www.audi-sport.net/vb/a3-s3-forum-8l-chassis/99273-how-log-vag-com.html which iv found very useful in explaining what it all means.
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  17. DJ_Troopa
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    DJ_Troopa K1 Driver

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    Thanks for that mate, i don't have vag-com so i'll get this done and logged by Bill. It's about time i get it properly logged and get it up to scratch! I've got my MOT and road tax due this month aswell!
    #17
  18. JtotheD
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    JtotheD Events Moderator

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    sorry to hijack, but how do u reset the DIS for the average MPG reading then?
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  19. DJ_Troopa
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    DJ_Troopa K1 Driver

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    Put the MPG mode on your DIS screen. There's a button under right stalk on steering wheel, hold that button and it will reset.
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  20. Westy
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    Westy Double Dark Side! Diesel & 8P

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    For an accurate MPG (the closest you can get to accurate anyway!) you should reset the MPG on the DIS every time you fill up with fuel.
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  21. JtotheD
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    JtotheD Events Moderator

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    or just work out what you are doing by diving the number of miles you've done by the gallons used!
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  22. DJ_Troopa
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    DJ_Troopa K1 Driver

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    I've never done that, i reset it on long journeys. I get 270-280 miles from a full tank but ever since this problem started i just got 228!
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  23. Westy
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    Westy Double Dark Side! Diesel & 8P

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    Yeah that works but we're talking about the DIS calculations. The DIS wont be accurate if you've left it for 3 years without resetting it as it'll be calculation from the last time it was reset.

    My old dear used to leave her astra and wondered why id never moved up or down. It hadn't been reset since the day she bought it and was now on 25K miles :lmfao:
    #23
  24. vrbob
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    vrbob Thats no Moon, Thats a space station!

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    Ouch 228 miles on a full tank thats really poor MPG i just put a tank through my car which was basically all town driving and just about managed 310 miles before the fuel light was on which works out as 24.91 MPG according to Road Trip lite app i use on my phone.

    Normally get about 28-30mpg (about 360ish miles to a full tank) which on my Dis says is 32mpg
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  25. DJ_Troopa
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    DJ_Troopa K1 Driver

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    Haha, i'll give that a go when i fill up later on!
    310 miles! I wish i could get that one day! Is that granny driving or giving it a boot now and then? lol
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  26. Westy
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    Westy Double Dark Side! Diesel & 8P

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    That might be un-mapped mate! I've hit 400 constant motorway miles when driving to Germany but under normal driving I'll see 240 - 260 MPG :(
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  27. JtotheD
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    JtotheD Events Moderator

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    I'm usually around the 270-280 mark. 100% town driving though. hardly get above 40 on my work journeys
    #27
  28. Nilz
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    Nilz Defo worth the wait :)

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    Aje

    You havent changed your fuel at all have you, what do you currently use?

    I noticed when I changed to V Power from normal Shell my MPG had a noticeable increase and a while ago when there was a V Power shortage and I used normal Shell unleaded, I could see a drop in miles and car feeling a little bit more sluggish.

    A shot in the dark, but you never know.
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  29. Alex C
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    Alex C Well-Known Member

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    my DIS is usually only 2% out on actuall (at the pump) mpg
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  30. StaceyS3
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    StaceyS3 Well-Known Member

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    I have been measuring my fuel consumption as really was doubting my dis as this is reading 21-23 as a running average but have been rather shocked since actually watching how many miles I get to a tank last 2 tanks I got 210 miles-55 litres and the last one nearly made me faint which was 170miles-56 litres
    I haven't even worked it out in mpg as I know it's rediculous and in the teens but that second tank was mainly pleasure drives giving the car some punishment ;-)
    #30
  31. jcs356
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    jcs356 Brum brum

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    The mpg on my old Ibiza dropped considerably when the crankcase breather pipe split. Assume the 1.8T has one so might be worth a check?
    #31
  32. Alex C
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    Alex C Well-Known Member

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    wells thats 17.4 and 13.8 mpg there

    do you have bigger injectors Stacey?
    Last edited: Jan 9, 2012
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  33. vrbob
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    vrbob Thats no Moon, Thats a space station!

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    Sub 200 miles wowsers thats impressive do you live life at 5000rpm and above??

    Mine is a Revo stage 1 with a few other mini mods (see my sig) but according to road trip i have filled up 11 times and am averaging 27.5 mpg and thats with the last 3 tanks all aboout 24mpg (or about 300miles) Got over 400 miles on a road trip the other week which is about 31mpg average which i thought was pretty good real world mileage.

    Average for my car is about 340-350 miles on a full tank so about 28-29mpg and thats 50/50 urban and motorway and a little fun here and there.
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  34. StaceyS3
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    StaceyS3 Well-Known Member

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    It does get abused and only really drive it for mainly pleasure as I work 2 miles from my home, but I suppose I do take a longer way home and quite often go for a 10 mile plus drive after work to have some fun as the roads are nice and quiet at 6 in the morning, ( there is some plus sides of working nights) ;-)

    Yes has got bigger injectors in there at the mo but I suppose it doesn't help that when driving it hard it spends a fair amount of time in the egt protection area dumping fuel, really would benefit me getting WMi sorted and should hopefully keep it in check ;-)
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  35. DJ_Troopa
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    DJ_Troopa K1 Driver

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    You guys and your MPG readings are killing me! I think i'll visit Bill in a couple weeks and get it checked over.
    #35
  36. Ian W
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    Ian W Active Member

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    I know just how you feel (luckily not with my S3) but my old 2L Corsa that I built up used to swallow a good portion of my money every single month, if it wasn't one thing it was another, over and over again for 5 years :-|

    Kept my S3 standard and tbh it's been pretty good :)
    #36
  37. S3 Paul
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    S3 Paul Active Member

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    I get about 330 miles per tank. stop start traffic and the odd friday night blast.
    My display went on a rather random reading session when i had a "loose connector" somewhere in the engine bay,
    I also suffered poor MPG when the fuel pump was ready for the knackers yard, I think this is because the injectors stayed open longer to try and sort out the low preasure issue. The car on both ocassions threw no codes up.
    #37
  38. Gops
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    Gops 6th gear @7000rpm

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    Would a throttle reset do anything for it? As In resetting it using the pedal?
    #38
  39. smokiedee
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    smokiedee Member

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    your not alone in a standard apart from bmc cda i get 22mpg recently but have had as bad as 17mpg on the trip mostly town driving like a granny with ocassional blast but very occasional. been doing my head in changed loads of stuff and still no better. get 200ish to a tank. and thats a agu a3 :(
    #39
  40. Teji
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    Teji New Member

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    DJ_Troopa - I though 19mpg in my car was bad !!!!!!!!!!!!

    Get that bad boy mapped and then when you hit 25 get that Micra Convertible you been after LOL
    #40

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