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  1. #1
    RichA3Turbo's Avatar
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    Hesitation/Misfire problem

    So... The past few days, i've been getting a misfire or sever hesitation around 2.5-3k RPM.... Only happens at part throttle...Anyone got any ideas? Going to investigate tomorrow.

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    Re: Hesitation/Misfire problem

    What about plugs Rich? Have they been changed recently?

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    Re: Hesitation/Misfire problem

    No i need to change them... But my though on that was they wouldnt mis at part throttle only...

    Rich

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    Re: Hesitation/Misfire problem

    If they need changing anyway then it may be a good place to start?

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    Re: Hesitation/Misfire problem

    I'm sure it's already crossed your mind, but I was really surprised a day or two before my coilpack went completly I had a very slight hesitation at 5.5-6k on part throttle, I only noticed because I was trying to see if AmD had fixed the rattle on my car (which they had). As I said on the other thread, I'm going to see if changing the other 3 has any effect on the smoothness of the engine assuming I can get them for less than the 28 I paid Audi for one!

    Take it you'll be trying the MAF etc, as that was what mine did almost exactely when the MAF went - it would be nothing nothing nothing... and we're off...

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    Re: Hesitation/Misfire problem

    Yep i did consider the coilpacks... Jay's A4 is same parts, so going to swap the MAF first, as that was first suspicion. If that doesnt work, then will swap the coilpacks. If not that, then the plugs....Cant see it being anything else really!

    Also going to check wiring .etc

    Rich

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    Re: Hesitation/Misfire problem

    RIch,

    You know what I have gone through with my S3 hesitation problem. At the moment, nearly 2 weeks after Torquing up the plugs, I have not had the hesitation. The car is bang on performance wise, it is truely unbelievable. Its like a rocket at the moment.

    My list would be:-

    1) Check your DV for smooth operation.
    2) Check your hoses, VAG-COM requested & actual boost, although if your mega modded like you are, IIRC it won't read correctly. (is that right?)
    3) VAG-COM misfires, logging all cylinders not just sum of misfires.
    4) take out the coil packs, check for discolouration and fitment. Do they fit snug still?
    5) whilst coils are out, look at plugs, colour etc. Do they look healthy. Change 'em if they've not been done for a while. S3 ones should last 40K, but if driven hard, or mega modded like your self, it might shorten their life.
    6) re-fit plugs Torque them to 30Nm .
    7) re-fit coils etc etc.
    8) Is the car any better? f not then check the MAF. Unplug it, is it any smoother? does hesitation occur.
    9) Perhaps clean the TB, and do an TB adaptation. I do this as a last resort, as when this is done, my car runs fine for about 3 weeks, and then hesitation comes back. (PS. when i did my plugs, i did not do an adaptation, didn't want it to skew my testing.)

    After that, you know the usual stuff, N75, N249, inputs to EPC, brake pedal light switch, clutch pedal switch, accel position sensor.

    good luck

    AL

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    Re: Hesitation/Misfire problem

    Thanks for that Al... Interesting about the plugs... Very odd in fact!

    Thats a good list. Boost is fine... 1.45bar... My car doesnt have a MAP sensor, so can not check boost with vag-com. Will check connection to my raclogic too, make sure that its not doing any weird thing with the injector signals. Will probably change the plugs anyway, as they were worn last time i looked a few weeks ago, but not got round to doing them...Dont think they are the issue though.

    Will try the easy swap stuff first and see how it goes

    Thanks

    RIch

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    Re: Hesitation/Misfire problem

    In the motronic manual, once you have checked plugs, coil-packs, it then suggests checking fuel delivery and pressure (hard job apparently) and injectors.

    It also suggests checking Fuel Supply relay, and power circuits to coil-packs and injectors. I'm still trying to learn how to do some of the stuff it suggests with a multi-meter. Can't find a good source of info or tutorials though.

    Good luck mate.

    AL

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    Re: Hesitation/Misfire problem

    Whilst we are on the subject of plugs. I recommend people with remapped cars try swapping their plugs to copper core items.

    The platinum core plugs are designed for long life and don't perform well for high boost applications.

    Reason being the plug core can't dissipate the heat from the core well enough to the cylinder head. The tip can start to heat glow and cause detonation.
    The knock sensors then detect this and back the timing and boost off. You can tell if this is happening if your boost surges under heavy load/full boost. Can be heard and seen on a gauge.
    Also spark can be blown out on this type.

    Copper plugs have thicker cores and conduct the heat away much quicker. Also larger spark. The copper plugs don't suffer from the issues that the standard plugs do.

    Downside of using copper plugs is that they wear out quicker, but they are cheaper to buy.
    I fitted a set to my car and my recent surging problems have dissapeared. Car boosts cleaner now and I can feel the difference.

    Also worth noting that if you are running over 50bhp over standard its worth thinking about buying a plug one heat range cooler.

    This is true for K03/k04s. I can't say if this is also true for IHIs, GT28Rs etc as you can get large power with less boost pressure.

    Worth trying at least once tho.

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    Re: Hesitation/Misfire problem

    Kev,

    Any particular brand/model?

    Rich

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    Re: Hesitation/Misfire problem

    HTC (kev?)

    Thats very interesting stuff mate. What plugs do you recommend? Plus, have you any more info on heat ranges? Does it normally say on the plug box?

    Cheers

    AL

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    Re: Hesitation/Misfire problem

    I'm running NGK - BKR7E at the mo. They are one range cooler. about 80 degrees cooler than the standard platinum/iridium.
    You could also try the BKR6E which is the standard heat range.
    Gap them at 0.8mm if they aren't already set.

    As for info, I studied a bit about spark plugs at college. But here's a webpage I found with a brief overview.

    Its all about keeping the plug at the right temps.

    http://www.ngksparkplugs.com/techinf...overviewp2.asp

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    Re: Hesitation/Misfire problem

    Well its not the MAF... And i've also checked the wiring to the coilpacks and they are fine. One thing i am going to check ias the racelogic box... See, i've taken the switched power for that from the headunit...But also on the headunit is the power for 2 gauges...I'm thinking that maybe i'm drawing too much on the single feed, and the racelogic is being underpowered!

    Rich

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    Re: Hesitation/Misfire problem

    Ok, so it wasnt the MAF, and it wasnt the racelogic being underpowered... New plugs should be here today, so will try that too.

    Rich

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    Re: Hesitation/Misfire problem

    fingers crossed

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    Re: Hesitation/Misfire problem

    I only ever notice it at part throttle (on boost) in 3rd gear... Very odd! If that doesnt solve it, then i'm gunna swap the coilpacks 1 by 1... Something has to solve it!

    Rich

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    Re: Hesitation/Misfire problem

    Just asked VAGParts for a price on the S3 coilpacks, there only 18 so I think I'll be replacing the other three in my car in the next month or two. The dealer wanted 28 by the way.

    Good luck getting it sorted rich.

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    Re: Hesitation/Misfire problem

    Thanks. Its not much of an issue...because i still got full power .etc... Just a bit of an odd issue!

    Rich

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    Re: Hesitation/Misfire problem

    Rich this is the same issue my car has (had hopefully). It always happens on part-throttle, on-off-back on throttle situations or when accelarating gradually, i.e. your right foot is being applied gradually and smoothly - almost slowly, not foot-to-the floor accelaration.

    In mine, the point of hesitation is just as the car feels like it is starting to produce boost. So not during spool up, but just as you feel the turbo is actually doing something. You know how you can feel the car loading up and start to push forward?

    Is that the same for you?

    AL

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    Re: Hesitation/Misfire problem

    [ QUOTE ]

    Is that the same for you?

    AL

    [/ QUOTE ]

    By the sounds of it (unfortunately!), yes! My ECU is less advanced than yours though... Its a different version of motronic...

    There are only so amny things it can be!

    Rich

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    Re: Hesitation/Misfire problem

    ahhhh, it's frustrating isn't it. Welcome to my world!! [img]/ubbthreads/images/graemlins/laugh.gif[/img]

    There are a few of us now Rich, I'm sure if we all share what we've tried, what works, what doesn't, we'll get to the bottom of it.

    There seems to be more and more folk having the same problem, regardless of car, TT, S3, A3 1.8T (pre and post facelifts), A3Q's. The lot. Not to mention Golfs and Leons. All the forums I have been to, its common, right across all 1.8T engines.

    AL

  24. #23
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    Re: Hesitation/Misfire problem

    You've gotta love motronic! [img]/ubbthreads/images/graemlins/10_1_114.gif[/img] Too many god damn sensors!

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    Re: Hesitation/Misfire problem

    This by the sounds of it is exactly the same problem I've been having for the last year.. and AL B [img]/ubbthreads/images/graemlins/smile.gif[/img]

    I posted it a while back and didn't really get anywhere. If you do ever find out what causes my missus would love you forever as shes the one that nearly hits the dash when it happens [img]/ubbthreads/images/graemlins/smile.gif[/img]

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    Re: Hesitation/Misfire problem

    Just a thought...It feels jsut like when racelogic cuts an injector pulse...Has anyone checked injector pulses?

    Rich

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    Re: Hesitation/Misfire problem

    I've not checked injector pulses yet.

    The other possibility is something causing the knock sensor(s) to kick in. But how you track something like that down, I do not know.

    AL

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    Re: Hesitation/Misfire problem

    [ QUOTE ]
    I've not checked injector pulses yet.

    The other possibility is something causing the knock sensor(s) to kick in. But how you track something like that down, I do not know.

    AL

    [/ QUOTE ]

    Unless the knock sensors are just knackered!

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    Re: Hesitation/Misfire problem

    Take a look at these:

    Audi A3 Lambda/Knock/Thrust/Impulse Sensors
    Audi S3/TT (BAM) Lambda/Knock/Thrust/Impulse Sensors

    All of these look like they would have an effect on the running... But what the hell is a thrust sensor!?

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    Re: Hesitation/Misfire problem

    Are those pages just a list of sensors, or are they all located around the ECU?

    No idea what thrust sensor is though.

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    Re: Hesitation/Misfire problem

    Just sensors, all in lambda control and anti knock .etc

    Rich

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    Re: Hesitation/Misfire problem

    OK..it appears the thrust sensor, is in fact the MAP sensor...not something i have to worry about!

  33. #32
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    Re: Hesitation/Misfire problem

    I think Elsa has a proceedure for testing these sorts of things. Might be worth a look.

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    Re: Hesitation/Misfire problem

    Any update Rich?

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    Re: Hesitation/Misfire problem

    Right...update.

    I changed the plugs on friday, before my MOT. Took it for MOT (Passed with flying colors! Its surprisingly environmnetally friendly!) And then on the way home, it was misfiring like a b*tch! I couldt get it to go over 2k rpm without is misfiring and kangarooing... Then, out of the blue, it stopped doing it, and started behaving again. What the hell is going on!? It appears to be only when its cold.

    Now 1 other thing i've noticed recently.
    1) When its cold, i get a coolant warning - No fault codes though (Ideas??)
    2) Coolant is not actually getting upto temp - Sits below 90o all the time (ideas again??)

    Thing is, the coolant warning i non specific...It refers to either coolant temp OR coolant level.

    I changed the coolant temp sensor about 18 months ago..and its not chucking any error codes or anything. But what else can mean that its not getting to temperature?

    Rich

  36. #35
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    Re: Hesitation/Misfire problem

    That sounds like a right pain, have you tried topping up the coolant level to stop the warning, I filled mine up so it was just above the correct level before christmas and I've not had the warning come on sinse (it was only doing it on very cold mornings)

    Just a thought as this might rule out that as a cause for the warning - I'm guessing it's got nothing to do with the actual running problems though eitherway.

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    Re: Hesitation/Misfire problem

    Yep, getting well p1ssed off with it now!

    The 15 year old mk2 GTi 16v sat next to the A3 on the drive is less of a pain!

    Rich

  38. #37
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    Re: Hesitation/Misfire problem

    Coolant warning is for dodgy sender on expansion tank most likely.

    Coolant temp issue either gauge or thermostat.

    Had this same coolant issue with mine last year. Swapped thermostat, now gauge always bang on 90.

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    Re: Hesitation/Misfire problem

    Although I'm not talking from experience... HTC may well be correct.

    From my various visits to different forums, after the coolant temp sensor, the actual Thermostat is the next best likely candidate for temperature issues...and possibly the sensor in the coolant expansion tank.

    There is a really good post on the TT-forum by "john-H", with step-by-step instructions...

    http://www.tt-forum.co.uk/ttforumbbs...ic.php?t=56316

    Hope this helps mate.

    AL

  40. #39
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    Re: Hesitation/Misfire problem

    Thats a great write up! Probably not the cause of my probs (misfore), but will replace the 'stat anyway.

    Rich

  41. #40
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    Re: Hesitation/Misfire problem

    When replacing the thermostat, be carful not to snap the oil dipstick holder like I did. Its very easy to do.

 

 
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