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HELP! New MAF now = crazy overboost and backfire through inlet!

Discussion in 'A3/S3 Forum (8L Chassis)' started by Prawn, Jun 16, 2011.

  1. Prawn
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    Prawn My other car is a MINI!!!!

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    [Jun 16, 2011]
    *WARNING - ANGRY PRAWN*

    AAAAAAAAAARRRRRRRRGGGGGGGGGHHHHHHHHHHH!!!!!!!!!!!!!!!!!!!!

    OK, so now that I've got that bit over, I need help folks :(

    You may remember my thread a few weeks ago:

    http://www.audi-sport.net/vb/a3-s3-...100%-likely-what-would-you-do.html?highlight=

    So, i got my money back, and yesterday, I went to euro car parts, and got myself a MAF from them.

    Threw it on last night, and FECK. Complete opposite result.

    I let the car warm up, then took it for a drive.

    Foot down in 1st gear, and it instantly felt flat, yet the boost appeared to rise to 20psi or so in first, despite there being very little 'pull'

    into second, and foot down, and boost instantly rose to 24-25psi, with absolutely no power at all, it just felt totally flat, and then there was a HUGE backfire, which appeared to come from the inlet!

    I did a bit more testing, and found that it backfires hugely when it comes onto boost, it's overboosting to 25psi or so, then when it backfires, I'm fairly sure it's comming back through the inlet, because as it does it, my boost guage jumps off the scale at 30psi momentarily! Scary ****.

    Easing the throttle in to stop the spike it feels totally flat on boost, and the whole car hesitates and feels like it's surging back and forth, still boosting 23-24psi, and still backfiring randomly whilst on boost.

    what the feck is going on? Do the AGU engines have any kind of Fuel cut that I might be hitting?

    I stuck my old maf back in, and it's back to usual, running 16psi max, but feeling WAY quicker than it did on the new ECP maf that gave me the 25psi spikes.

    I thought at first it was because I've over tightened the wastegate arm in the past, but on actuator pressure it runs 6psi just as it should :(

    I don't get it guys :( First two mads gave me no extra boost at all, now this one has gone the otherway, into epic over boost, yet it feels flat as anything, so I'm sure it's pulling out all the timing.

    Will try and log it tonight and see where it's going wrong.

    Not happy at all :(
    #1
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  3. s3dave
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    s3dave TFSI Hybrid

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    [Jun 16, 2011]
    All i can think of is the ignition amp module breaking down from the new airflow..?
    Is your connector ok that goes into the MAF the pink insert can snap and cause the connectors inside to touch...
    #2
  4. Prawn
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    Prawn My other car is a MINI!!!!

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    [Jun 16, 2011]
    Hmmmmmmmmmmmmmmm, that's not a bad shout Dave, connectors look fine, old maf in and the car drives perfectly.

    What gets me though, is, like I said in my last thread: with Plunkys MAF fitted the car runs amazingly, and runs the 22psi it was mapped for perfectly :(

    Backfire through the inlet is not something I've had on a 20vt before. mini has done it in the past, but that's always a timing issue.
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  5. s3dave
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    s3dave TFSI Hybrid

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    [Jun 16, 2011]
    Yeah usually timing or sticking valves, weird one..
    #4
  6. Welly
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    Welly VX220 SC Driver :)

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    [Jun 16, 2011]
    Just a thought dude - what engine is Plunky's?
    #5
  7. Welly
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    Welly VX220 SC Driver :)

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    [Jun 16, 2011]
    Saw this and thought of you....

    [​IMG]
    #6
  8. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Jun 16, 2011]
    what does it read g/s wise?
    backfire is lean backfire, so most likely dodgy maf again, and daft signal regarding airflow, for which the ecu's fueling against
    #7
  9. Prawn
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    Prawn My other car is a MINI!!!!

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    [Jun 16, 2011]
    AGU again, same engine, same ko3S, even the same exhaust and FMIC.

    Cheers Bill, I was hoping you would read this!

    I was thinking it could be a lean backfire, bit scary that, as it sounds like it's pretty risky running it at all.

    not logged it yet, will log this evening if I dare try it again.

    the odd thing is, my old MAF was (and still is) giving 187 g/s, which as I understand, is pretty epic flow for a ko3S, yet it'll only give me 16psi of boost. Plunkys maf in the car and I'm getting a really nice solid 22psi hold, and it's WAY quicker. Not had a chance to log with Plunkys yet.
    #8
  10. 666markyboy
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    666markyboy Well-Known Member

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    [Jun 16, 2011]
    Have you tried your MAF in Plunky's car ?? i'm sure i read on here somewhere only to buy MAF's off the stealers as the aftermarket ones seem very dubious,,, sure someone said they tried 4 replacements from GSF before they fianally went to Audi to get one that worked properly
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    fran-s3 likes this.
  11. Sandip
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    Sandip Well-Known Member

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    [Jun 16, 2011]
    Prawn have you got N75J valve?
    #10
  12. ja3mie
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    ja3mie A3 1.8t Quattro Sport!

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    [Jun 16, 2011]
    rather than trying other peoples on yours.. try yours on other peoples!

    if theres plays up.. its 100% the maf.. if you put theres on yours and its fine... did you knock a wire that may be loose etc etc :)
    #11
  13. fran-s3
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    fran-s3 Active Member VCDS Map User

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    [Jun 16, 2011]
    Always buy a MAF from the stealers - one of the few items that it's worth spending the extra ££ for a genuine one.
    #12
  14. Dane
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    Dane Faster than a V12 Q7

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  15. Sam_
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    Sam_ Down under

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    [Jun 16, 2011]
    #14
  16. Prawn
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    Prawn My other car is a MINI!!!!

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    [Jun 16, 2011]
    Not tried my maf on plunkys car yet, need to speak to him nicely!

    No n75J Sandip, all standard!

    I just don't get it, first few give me no boost, the this bastard sends it crazy!
    #15
  17. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Jun 16, 2011]
    I've had bad experiences with sensors from ECP before so anything elextrical I get from Audi.

    You'd better not tell Plunky that your new MAF might blow his car up shhhhh ;)
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  18. Prawn
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    Prawn My other car is a MINI!!!!

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    [Jun 16, 2011]
    Problem is dude, a new MAF for mine at audi is MEGA money! trade price from TPS it's £231, so I think audi would be even more! (audi get their parts from TPS)

    Sadly they don't do exchange on these 4 wires MAFs, so it's outright only at crazy expense!
    #17
  19. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Jun 16, 2011]
    Oh yes you have told me before, my memory is dreadful!
    #18
  20. NHN
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    NHN Retrofitter - Audi - VW - Skoda - Seat Site Sponsor VCDS Map User

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    [Jun 16, 2011]
    I reiterate whats been said, always get a maf from audi, would never entertain from anyone else for this specific part, as quite simply I dont trust the mafs from others.
    #19
  21. ja3mie
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    ja3mie A3 1.8t Quattro Sport!

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    [Jun 16, 2011]
    does it run without the maf connected?
    #20
  22. Prawn
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    Prawn My other car is a MINI!!!!

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    [Jun 16, 2011]
    OK, did some testing tonight, and I THINK Bill has got it spot on, check out these logs:

    [​IMG]

    On my old dead maf, going full throttle around 3k, at about 4k I'm getting 140g/s+

    With the ECP maf, same road, 5 minutes later, going full throttle at 3k again, at around 4k I'm only getting between 85-105 g/s.
    Massive reduction in g/s at near identical RPM's, I couldn't risk taking the car to higher RPM's with the ECP maf as it felt SERIOUSLY rough.

    I guess, if the new MAF is reading really low, the car thinks it hasn't reached it's target load, so asks for loads more air to get where it wants to be, hence the low boost, and the lean misfire is because it's still fuelling from the MAF readings, so going mega lean?

    Thoughts most welcome!
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  23. Prawn
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    Prawn My other car is a MINI!!!!

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    [Jun 16, 2011]
    Just looked back through some old logs, and it's always been around 140g/s at 4k in the past, so this new one giving ~100g/s at 4k is HUGELY under reading. I was also getting a 'maf signal too low' fault code.

    this HAS to be the problem surely?
    #22
  24. Pat
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    [Jun 16, 2011]
    Andy from Lincoln VW spec has been out mapping my BT engine this week.. did afew runs then all of a sudden dash lit up like a xmas tree.. this was down to the MAF.. Been to tps and got a new gen one.. worth the extra pennies
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  25. Prawn
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    Prawn My other car is a MINI!!!!

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    [Jun 16, 2011]
    £230 though! That's mental money for a bloody maf :S
    #24
  26. NHN
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    NHN Retrofitter - Audi - VW - Skoda - Seat Site Sponsor VCDS Map User

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    [Jun 16, 2011]
    & how much you putting in your tank weekly :p still whining & get that maf baby fitted lol
    #25
  27. Prawn
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    Prawn My other car is a MINI!!!!

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    [Jun 16, 2011]
    Quick vid showing the overboost and backfires. They seem really tame on the video, but are infact pretty violent in real life!

    I don't back of the throttle between the two pops in the second pull, it does that all on it's own.

    If I hold my foot down through the pops, the car pulls VERY sluggishly, and feels awful, surging back and forth, although the boost remains high:S

    YouTube - ‪A3 turbo overboost. Dead maf suspected‬‏
    #26
  28. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Jun 16, 2011]
    Ooo nice airflow readings, you might as well bring danes micra to the ring in September ;)

    Seriously though MAFs are so god damn important on these cars and it does seem that there are a lot of bogus ones around.
    Last edited: Jun 17, 2011
    #27
  29. S3 Nattie
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    S3 Nattie Quattro ist für sissies

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    [Jun 17, 2011]
    Your turbos working hard ini, 99.6 duty cycle throughout most of the rev range
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  30. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Jun 17, 2011]
    I had this once with ebay MAFs, only cure was to bite the bullet and buy one from the stealers. PS also cost me a turbo m as i "lost" a jubilee clipp during swap, and the turbo consumed it GULP

    Expensive MAF that was.....
    #29
  31. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Jun 17, 2011]
    Bloody hell. I bet you double check from now on.

    It's funny you should say this because when I fitted my B5 TIP last week on my brand new (only done 200 miles) turbo, one of the small jubalees had dropped into the bottom of the TIP! Luckily it was spotted before putting the top hose on :faint:
    #30
  32. JamJay
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    JamJay Member

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    [Jun 17, 2011]
    I have no idea what your car is running but £230 for a MAF? Surely not...what is it from?
    #31
  33. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Jun 17, 2011]
    maf looks faulty to me dude
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  34. Dane
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    Dane Faster than a V12 Q7

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    [Jun 17, 2011]
    :lmfao: you cheeky mofo, it's actually my brothers thanks ;)
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  35. sportstractor
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    sportstractor Chugger

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    [Jun 17, 2011]
    Don't be a tightarse mr iv got 3 cars ;)
    #34
  36. Prawn
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    Prawn My other car is a MINI!!!!

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    [Jun 17, 2011]
    Cheeky bastard! It's quicker in a straight line than a stage 1 S3, so we shall see :p

    standard MAF for an AGU engine, very early 1.8T from 97/98, it runs ME3.8 ECU as opposed to ME7 in the newer cars, and has a 4 wire MAF instead of the 3 wire MAF in later cars. Audi/TPS no longer sell them as exchange items, and offer an outright sale only.

    Cheers Bill, I'm hoping so!

    Just been down to ECP with all my logs in hand, the bloke didn't question my results at all (and rightly so), So I've now got MAF # 4 to test tonight!

    if this fails, then I'll be paying the £230 for a new one from TPS
    #35
  37. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Jun 17, 2011]
    No we wont because I'll be stage 2 in 2 weeks time :p
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  38. 666markyboy
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    666markyboy Well-Known Member

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    [Jun 17, 2011]
    Hmmm i wonder what sort of MAF it is on my 99 AJQ engine ? hope it's not an expensive hard toget hold of one like yours Prawn.. I'll have to check that out this weekend..... when you say 4 wires do you mean going to the plug that plugs into the MAF of that it has 4 wires inside ???
    #37
  39. Prawn
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    Prawn My other car is a MINI!!!!

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    [Jun 17, 2011]
    yea, my AUM has a 3 wire maf, when you pull the plug there are 3 pins. 4 pins on the AGU maf

    Westy: I'll be dead keen to see just how much quicker your st2 S3 is than my St2 A3, will be very interesting!
    #38
  40. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Jun 17, 2011]
    I'd expect yours to be quicker over all due to your lack of weight. Straight line might be very close though.
    #39
  41. Prawn
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    Prawn My other car is a MINI!!!!

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    [Jun 17, 2011]
    Point to point, considering the work, I'd be mortified if it wernt quicker :p mainly due to weight / brakes more than anything.

    Meh. who cares, so long as we enjoy them :D

    Will try and test maf tonight, but it's raining, and my lack of haldex prevents wet weather fun :(
    #40

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