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Help needed!..3.2Q DSG Hesitant engine ~ 2k rpm

Discussion in 'A3/S3/Sportback (8P Chassis)' started by 3.2 Ju, Aug 26, 2009.

  1. Coxylaad
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    Coxylaad Member

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    [Feb 9, 2010]
    throttle body changed tonight when i got in. ecu reset and throttle adaptation performed.
    no change at idle.

    i didnt get a chance to test drive it, but by the feel of it its exavtly the same.

    I think we are definately down on part throttle power below 2k rpm

    looks like its oil pump next then i have done everything!!!
  2. 3.2 Ju
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    3.2 Ju Well-Known Member

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    [Feb 10, 2010]
    Bugger! Was lining that up for my final fix!!
    I definately think the oil pump has made a big difference on mine though. One of the causes of a stretched chain (which mine had) is believed to be the bypass valve in the oil pump which malfunctions and blocks putting too much pressure into the system. As the vvt's and tensioner work of oil, any variation from normal must have some sort of affect
    If you can read german then download this 157 page pdf detailing the problem, it includes some great pictures

    http://www.a3quattro.de/pdf/Bericht_VR6_3-2_Kettentrieb_onlineVers.pdf
  3. Coxylaad
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    Coxylaad Member

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    [Feb 10, 2010]
    well hold the bus. I drove it to the garage this morning to get the tracking done, and the car was definately a lot smoother. I can tell crawling off from a stand still, the revs used to do nothing, then lurch forward. No surging or anything, but the weather was terrible and I never got over 40mph.

    I will be picking it up before dinner so I will report back. It may have been that it needed a drive to clear the plugs up or something?

    If it doesnt work then this is my theory about the oil pump - and its different to what everyone thinks. I believe the oil pump is not providing enough pressure at low rpm. Not enough to cause any engine damage, but insufficient to hold the vvt cam in its advanced position that it should be in at low rpm. Once past 2000rpm the engine has enough oil pressure to operate correctly, and shortly after that the cam timing changes anyway. This would explain the poor fuel economy, as with the wrong cam timing at low rpm the engine is getting no cylinder fill, also explains how full throttle is fine as it just chucks loads of fuel in.
  4. edition
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    edition Active Member

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    [Feb 10, 2010]
    Let us know Coxy!!
  5. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 10, 2010]
    I'm still sure my problem is the TB if only because if it start up and its messing about then switching off and re starting does the trick and we know the TB does a sweep to reset on ignition on. I am sure this is not a map problem because my engine was fine on this map for 40k mile. If it was my oil pump i would expect it to get worse with a hot engine but in reality its worse when cold ie thick oil.
    That said i am open to any ideas :)

    This intresting, i stole it of another forum about the Audi TT.....read the bit about the lambda sensor !!!!!

    Hunting problems, where the engine speed rhythmically varies, can be caused by an air leak on the intake manifold side of the throttle body. This includes the various vacuum lines going to various places. Check for leaks. Spraying WD40 onto suspect areas can help diagnosis as it will get sucked in and burnt and cause an engine speed change. Clamping any rubber vacuum hoses can help too as can using a spare rubber hose as a stethoscope and listening for hissing and whistling.

    An unstable idle can also be caused by a dirty throttle body. The walls of the body can become built up with dirt and upset the carefully controlled surface profile needed when the throttle is nearly closed, causing a large or sudden variation of open gap area with small angles of throttle butterfly movement. This tends to cause an erratic idle as it upsets the idle control loop.

    A faulty (slow but not dead) lambda sensor can produce an unstable idle and also make it difficult to hold the revs constant at 2,000 or 3,000 rpm etc. as it will tend to suddenly change a couple of hundred rpm as the mixture snaps from being rich to lean etc.

    There is also an engine RPM speed sensor G28 next to the throttle on the end of the inlet manifold. It has a 3-pin connector with pin 1 next to the flat end with the tab.

    Measure between pin 2 and 3 with a multimeter set to resistance. You should get 730 to 1,000 Ohms at 20 deg C. Resistance increases as temperature increases.

    Also measure between pin 1 and 2 and pin 1 and 3 - in both cases it should be open circuit.

    If the above isn't obtained replace the sensor.

    Coilpacks suffering partial breakdown and a weak spark - and this can last for months before eventual failure - may cause uneven idle, lack of power and jerking acceleration with sudden late turbo (similar to faulty MAF symptoms) as well as occasional intermittent misfire as a clue.
  6. edition
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    edition Active Member

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    [Feb 10, 2010]
    3.2 tt?
  7. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 10, 2010]
    He dosnt say, he is talking in general.
    Interesting because i had a lambda sensor fail and replaced not long before my troubles began.
  8. 3.2 Ju
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    3.2 Ju Well-Known Member

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    [Feb 10, 2010]
    No Paddy, mines perfect when the engine is cold, holds revs and drives sweet as a nut, it's only when the engine warms up that the troubles start!
  9. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 11, 2010]
    no one seems convinced by the lambda thing then ?
  10. Coxylaad
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    Coxylaad Member

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    [Feb 15, 2010]
    well initially i thought the TB change had made a huge difference, the car was smooth and tractible, and fault free.
    But it appears to have re learned its fault again...
  11. 3.2 Ju
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    3.2 Ju Well-Known Member

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    [Feb 15, 2010]
    Yep mine is still doing it although it is a lot better since the oil pump change. I suspect the pump may have been faulty causing my timing chain to stretch and that could have also been amplifying the hesitation.
    Not sure on where to go with this now, maybe as Paddy says, it could be lambda?
    Had the 16398 Camshaft set point not reached fault back again at the weekend as well!
  12. 3.2 Ju
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    3.2 Ju Well-Known Member

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    [Feb 15, 2010]
    I also called at Awesome on Saturday for the APR trial but the map wasn't available for my ECU so they read the current map from it and have sent it off to APR in America to have one made. Not expecting it to make any difference tbh but it's something I want to do anyway!
  13. edition
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    edition Active Member

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    [Feb 16, 2010]
    Nice one Julian let me know about that, I might get mine done...
  14. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 18, 2010]
    I would be wary of a remap...had mine done but it was a waste of money really. not the sort of gains you would ever notice on the road.

    As my start up tick over problem gets worse I am now thinking it could be damp !! hence its fine once its done a few miles and only plays up when its been standing all day or all night. Its a pig to keep it running as its DSG and you cant dip the clutch and catch the revs. But i drove about a mile this morning and it was playing up, when i parked it was stalling and just catching its self with a 500rpm burst...then stalling again. switched off called in a couple of shops and came back and it runs like a watch again.........maybe it had time to dry out ?? I will give it a spray with something this weekend, dont know what but it might help..........the story continues....:faint:

    Oh...and get a before after dyno test or you will not know if its done anything...
    Last edited: Feb 18, 2010
  15. 3.2 Ju
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    3.2 Ju Well-Known Member

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    [Feb 18, 2010]
    TBH Paddy, I'm not bothered about the remap side of things as I know the gains are marginal at best, it's the anti-theft that I'm really wanting to take advantage of as I had it on my Leon Cupra R and thought it was great. All these stories about Audi's being stolen is starting to make me paranoid lol!
    I'm also thinking that you're problem is a little different to mine as mine is faultless when cold for about the first 5 minutes or so, I do think you're right though and lambda is the next point of call.
    I've been trying to think what makes this hesitation issue specific to the 3.2 and only the A3 at that (or so it seems!) Would I be right in thinking that it's the only A3 with 4 lambda probes instead of 2, 2 pre cat and 2 post cat? Surely there will be something in VCDS to log the output values.
  16. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 18, 2010]
    I think we have the same problem...just that i have 2 problems. You are right , my car will hold 2k revs when cold/first start up...but after a few minutes it starts its popping and banging through the exhaust and has the 2k hesitation on the road. I'm convinced now its Lambda's but i think i will try the front 2 first as they are the most likely to oil/soot/ break down first and my problems certainly started after i had one changed for another reason.
  17. Coxylaad
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    Coxylaad Member

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    [Feb 19, 2010]
    the front 2 lambdas are the ones that do the engine trimming, the rear 2 are only there for checking the condition of the cat.

    My car is as jerky as it was before I changed the throttle body.

    oil pump next then.

    Julian Have you changed your VVT solonoids?
  18. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 19, 2010]
    Copy of letter sent to John at Audi TT forum

    Hi John.
    Forgive me for contacting you but while doing a google search for Audi throttle body i came across this post of yours...
    A faulty (slow but not dead) lambda sensor can produce an unstable idle and also make it difficult to hold the revs constant at 2,000 or 3,000 rpm etc. as it will tend to suddenly change a couple of hundred rpm as the mixture snaps from being rich to lean etc..

    I have a 3.2 A3 and like quite a few others at Audi sport .net we have this 2k misfire.
    Our thread has reached 500 posts and 10 pages now and we have spent £ 000's trying fix this problem that shows no fault codes etc.. throttle body's /VvT sprockets/vvt solenoids /cam chains/fuel pump relays/oil pumps and so on have been replaced to no avail. Now i see your post re Lambda and i wondered if you were
    A/ thinking 3.2 V6
    B/ If anyone has cured the problem by replacing the first 2 Lambda probes ??

    http://www.audi-sport.net/vb/showthread.php?78089-Help-needed!-3-2Q-DSG-Hesitant-engine-~-2k-rpm

    Any help you cam give us desperate A3 owners would be most welcome :))

    Many thanks
    Paddy
  19. 3.2 Ju
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    3.2 Ju Well-Known Member

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    [Feb 19, 2010]
    Yes Ian, Everything has been changed VVT's, VVT Housing, Cam sensors, both chains, all guides sprockets and tensioners, Maf sensor, Oil pump, Oil and filter change with Mobil 1 and fuel filter.

    TBH I wouldn't expect the oil pump to make a huge difference, I'm pretty sure mine runs better but the fault does seem to relearn itself after a short while
  20. 3.2 Ju
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    3.2 Ju Well-Known Member

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    [Feb 19, 2010]
    Fingers crossed, I think we could do with a little outside inspiration:idea:
  21. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 19, 2010]
    Reply from John...

    Hi Paddy,

    It sounds like a classic control loop problem where something is introducing noise or delay into the loop but what exactly can be a tricky thing to find out. Here are some things which may help:

    Firstly, not everyone declaring this problem may have the same cause as different causes can have the same effect – so there may not be one simple fix for all – but possibly most could be covered by a single issue. So don’t rule out a possibility if just one person confirms a particular item is not his cause.

    The ECU monitors a number of items and tries to keep engine speed constant against load at a certain throttle position. Presuming the throttle position sensor is good and constant (as there are two within and each is monitored against the other in an effort to detect a fault, so is unlikely to be the issue here), then what effects engine speed is basically mixture and timing.

    At constant engine speed the MAF should be out of the loop (as it’s only used during acceleration when the lambda brobe is saturated by the rich mixture necessary for acceleration) and the ECU is just looking at the lambda value, to get an idea of the mixture and the crankshaft position sensor, to know when to fire the spark. Any variation or noise in these two sensors will directly affect combustion and alter the energy being released from the fuel used to overcome friction and hence affect engine speed. This could be a lazy lambda that only changes slowly (you need to look at this o an oscilloscope as the ECU may not flag up a slow response) or a loose or intermittent high resistance crank sensor which can cause scatter of the timing and poor combustion.

    Poor combustion can also be caused by weak coil packs or plugs, leaking fuel injectors or manifold air leaks (exhaust or inlet) which can cause the lambda to read rich and have the ECU weaken the mixture in an effort to correct the air/fuel ratio. You see how these things can be interrelated? The engine temperature sensor can play a part here too as if the ECU thinks it’s cold it will enrich the mixture – so check this sensor too and wiring for loose contact.

    Other things could be camshaft position sensor which also affects timing and include in this slack chains/belts causing scatter. Engine earthing can also be an issue as excess electrical noise can cause false or noisy readings of otherwise good sensors.

    Dirty throttle bodies can be prone to cause a lumpy idle due to the difficulty the ECU has in creating a linear change in opening with butterfly angle – particularly when almost closed. This is because the throttle body in the vicinity of the butterfly edge needs to be smooth and precise and lumps of carbon or oil deposits make the progression irregular and effectively add gain variation (classic control theory) into the feedback loop with the ECU.

    Sometimes improving one item seems to effect a cure but then it comes back because you didn’t fix the biggest problem but instead just helped the ECU regain marginal control e.g. improving engine earths with thick straps reduces sensor noise but you’ve still got a dirty throttle body or blocked vacuum line or air leak.

    Relying on the ECU to generate fault codes is not always helpful as sometimes a sensor needs to completely stop giving a signal for the ECU to log a fault. That’s why looking at sensor signals directly with an oscilloscope or multimeter will often reveal where the noise is in your feedback loop.

    I hope that helps.

    Regards,
    John
  22. Coxylaad
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    Coxylaad Member

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    [Feb 19, 2010]
    i thought someone had already changed the lambda probes?
  23. edition
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    edition Active Member

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    [Feb 19, 2010]
    This may get us all off the scent but I have noticed sometimes mine does it (the hesitancy at 2kish on light load) and the car is fully warmed up but the temp needle is say 1mm off the middle on the guage........... Could this be a sendor telling the car that it's not warm yet and f'ing the fueling up??


    Has anybody else noticed this?
  24. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 19, 2010]
    Possible you have sticky thermostat J

    More from the TT forum..

    Thanks for that John.
    Our problems do seem remarkably similar in the A3's in that they all run fine at first start up from cold for a few minutes and the deteriorate with engine temp. They mostly have done between 40-50k miles. Mine pops and bangs in the pipe at 2k ( if you can hold 2k) and Audi say its simtomatic of the engine but the way the car and engine shake its obviously misfiring. I have run blocks with VCDS on it several times but cant find anything amiss. That said mine got worse after the last long life service which could point to the new plugs...but others have changed them without result.
    We mostly feel that Audi have left us to do our own research on this because they refuse to accept there is a problem and yet take it to an independent and they contradict that without question....
    Thank you for your time and taking the trouble to reply
    All the best
    Paddy


    Pops and bangs suggest scattered timing rather than incorrect mixture. I'd look to coilpacks and wiring for shorts and crankshaft sensor (speed sensor).

    Regards,
    John
  25. Coxylaad
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    Coxylaad Member

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    [Feb 19, 2010]
    well I have new plugs and I have swapped loads of coils about, so there is only the engine speed spendor left. Not sure how to test that!
  26. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 19, 2010]
    It seems its near the oil filter and is held in by one screw. Its a magnet and can pick up **** wich means it gives out false readings. not worth replacing but well worth cleaning i gather ?

    this is it
    http://www.worldimpex.com/assets/partimages/045176.jpg

    Interestingly it controls the fuel pump relay...
    Last edited: Feb 19, 2010
  27. edition
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    edition Active Member

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    [Feb 19, 2010]
    How much are they too buy new? If there not much £££ it might be worth fitting new....
  28. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 19, 2010]
    I think about £60 but the point is its just a magnet so if you clean all the metal scraps off and oil ect it it should be ok. If it had failed completly your engine would not run.
  29. edition
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    edition Active Member

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    [Feb 19, 2010]
    But what happens I'd it hasn't failed fully and if giving spurious readings at times ....
  30. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 19, 2010]
    It cant really fault other than fail completely. its just a magnet. that picks up pulses from another magnet on the crankshaft. It can however get dirty or pick up metal particles that could give a false reading. So cleaning should fix it. If it has broken then the car would not run at all
  31. edition
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    edition Active Member

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    [Feb 20, 2010]
    How easy a job is removal???
  32. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 20, 2010]
    not sure, still trying to find its exact location with ELSAWIN but the search facility is ****. It seems it just fits in with one cap head. On the 18T its next to oil filter and accesable from underneath...but thats not a lot of help to us..
  33. edition
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    edition Active Member

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    [Feb 20, 2010]
    Hmmm let me know when you find it...

    Does it mean we would need to do it when replacing the oil?? I.e oil will pour out when removed?
  34. 3.2 Ju
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    3.2 Ju Well-Known Member

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    [Feb 20, 2010]
    its right next to the oil filter. I found it on elsawin but its not listed separatel as such, its on the diagram with all the engine sensors. Once the tray is removed from underneath, the filter is right at the front.
    I checked the measuring blocks this morning for engine speed (g28) and the rev counter on mine was reading slightly low (approx 40) and it did jump around quite a bit , maybe 80rpm or so.
    Let me know how you get on as I'm away this weekend
  35. 3.2 Ju
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    3.2 Ju Well-Known Member

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    [Feb 21, 2010]
    Took the sensor out tonight and cleaned/put it back and it made no difference. Tbh there wasn't anything to clean as you can see in the picture.
    [​IMG]
    Mine is still behaving itself a lot better and drives near faultless now, but i'd still like to get to the bottom of it though as it niggles away at me that it won't hold the revs as it should:think:
  36. paddy
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    paddy Audi=No fault code, no idea

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    [Feb 21, 2010]
    Well done Ju...we can cross that off the list then.

    You have to wonder if it is not just a map problem. We know the timing advance starts at 2k rpm, we know remaps only start at 2krpm..and we know that when cold with the timing advanced ( as part of the choke sequence) it runs ok as well.
    Could it be that the std timing at 0-2000rpm is just to far retarded ? and this shows up as things wear ?? Its a shame we cant get a couple of degree's advance mapped in to the program.
  37. edition
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    edition Active Member

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    [Feb 21, 2010]
    Yeah good work Julian! Was too cold for me today

    paddy glad you have come round to my remap thinking and that Julian has sorted a new map!!

    Just want to get my head round the map only works above 2k.. How did they sort this on the r32 as this was in our rev range....
  38. Coxylaad
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    Coxylaad Member

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    [Feb 22, 2010]
    why does it just do it with certain cars and not all of them then?
    I have tried another ecu in my car and it was exactly the same.

    If it is the map then if anything its too advanced below 2000rpm. when you retard the timing if becomes sluggish and slow revving, but its usually still stable in my experience. And if you think about it, when you reset the ecu it goes back to its base values, and over time starts to advance the timing to the best acceptable point, re introducing the condition.

    thats how i see it anyway. its got to be a component.
  39. mr_maj
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    mr_maj New Member

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    [Feb 22, 2010]
    DSG Selector Module Fault?? Anyone checked this out?
  40. mr_maj
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    mr_maj New Member

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    [Feb 22, 2010]

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