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Thread: ecu reset mk4

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    Default ecu reset mk4

    hi i recently done a ecu reset to try and sort the problems on my car i have been told if you dissconnect the battery for 24hours the ecu will go back to stanard and set itself all back up is that right?? also does it matter wat terminals you take off as i took off the possitive one not the earth should this make a difference??

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    bump anyone??

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    Someone Must No Or Have A Idea!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!plz Help Me!!!

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    Try uk-mkivs.net has loads of info on there for MK4 and 5's
    its not a car its a volkswagen

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    From what i have read its a couple of hours. Any fault codes will soon come back when you drive the car though. Its not a fix
    its not a car its a volkswagen

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    To do an ECU reset on my Skoda RS, which has the same 20v lump in as the mk4 golfs just a bigger turbo, you disconnect the battery for a couple of hours, re-connect, then switch ignition to position 2, the throttle body should squeal for about 10 seconds. After the throttle body shuts up, switch off the ignition, then fire up the motor but don't touch the accelerator at all for 10 min's. After 10 min's take for a spirited drive as the ECU is an adaptive unit and needs to learn new things e.t.c. Hope that helps

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    ok thankyou do i have to dissconnect the possitive or the negative or will it not make a difference??? also wat is possition 2?? how longshall i leave it dissconnected for?

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    Disconnect the negative terminal for about 2 hours, it may be worth switching your lights on while the battery's off too, just to make sure that the ECU is totally drained of power. Position 2 is the second click on the ignition, just before the starter motor fires up. Don't forget to let the engine idle for 10 min's before you touch the throttle when you start it after the reset, then go out and have a nice fun drive.
    Last edited by marty1979; 11th March 2009 at 16:54.

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    ok cheers buddy will it matter weather i disconnect the negetave or the possitive???? as i disconnected the possitive and it didnt do anyhting. please help cheers m8

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    It shouldn't matter which terminal is removed really, I usually take the negative off though. What are you expecting to happen when you reset the ECU? Normally a reset should be done after installing an aftermarket air filter, or have an after market exhaust fitted e.t.c. You mention earlier that you're having prob's with your car, a reset will clear codes but if there's a fault somewhere it will just flag again. What's up with your motor, I'll try and help you out if I can

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    ok mate well its basicaly runnin real slow recently. so i plugged it into vag.com and it said i have a faulty cold water temp sensor so i changed that and now the car runs really cold wont even go up 2 90 on the gauge!!! it did before.. any ideas i dont think the thermostat is stuck open as it was fine before i changed it i only changed it cause vag.com picked up that as a fault!!! but basicily i just think it runnin a bit slow and now its runnin really cold i have unplugged the maf sensor and took it for a drive and it makes no difference to the preformance which is strange? can u help?????

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    dis connection will only clear the 'low' memory which include the basic settings & possibly the actual light on
    fualts will still be stored

    best thing is do get it plugged in, what stored fauts are there? thermostat issue?? heaters hot? very likely to coolant temp switch
    CGTI Member #4026 Mk 1 TDI, Mk 1 1.6 GTI, Mk 4

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    ok mate well its basicaly runnin real slow recently. so i plugged it into vag.com and it said i have a faulty cold water temp sensor so i changed that and now the car runs really cold wont even go up 2 90 on the gauge!!! it did before.. any ideas i dont think the thermostat is stuck open as it was fine before i changed it i only changed it cause vag.com picked up that as a fault!!! but basicily i just think it runnin a bit slow and now its runnin really cold i have unplugged the maf sensor and took it for a drive and it makes no difference to the preformance which is strange? can u help?????

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    If there is no change in driveability when the MAF is unplugged, then that would suggest a faulty MAF sensor. Do you have a K&N filter on the MAF? If so then the oil from it could've fouled the wire which reads air temperature. It can be cleaned but I'll run that by you later if it isn't completely dead. Usually the engine will stumble when you plug the connector back into the MAF, if nothing happens then the ECU is probably ignoring it completely and using a basic map, which is why the car feels slow. Also there is a pipe that comes off the bottom of the turbo that is known for leaking air, you'll see it if you get under the car and look up at the turbo, tell tale sign is oil running down the side of the pipe.

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    Quote Originally Posted by marty1979
    If there is no change in driveability when the MAF is unplugged, then that would suggest a faulty MAF sensor. Do you have a K&N filter on the MAF? If so then the oil from it could've fouled the wire which reads air temperature. It can be cleaned but I'll run that by you later if it isn't completely dead. Usually the engine will stumble when you plug the connector back into the MAF, if nothing happens then the ECU is probably ignoring it completely and using a basic map, which is why the car feels slow. Also there is a pipe that comes off the bottom of the turbo that is known for leaking air, you'll see it if you get under the car and look up at the turbo, tell tale sign is oil running down the side of the pipe.

    yes mate it has got a airfilter on it but its on the end of a long carbon pipe behined the front bumper. so u could be right how do i clean the maf? i have wiped it out with a rag before i dissconected the maf sensor wen the car was runnin before and it did splutter and cut out then it would restart and run ok but still slow. then wen i plugged it back in it spluttered again. how do i tell that if the maf is dead??? what will i need to do to fix it?? any ideas buddy??? u seem to no ur stuff

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    You cant clean a maf and if you have tried then you have moe than likely destroyed it

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    Disconnecting the MAF is a myth.

    Cleanig the MAF is a very short term solution. You can clean it by spraying it with electric contact cleaner. http://uk-mkivs.net/forums/p/18018/532522.aspx#532522

    Does your car have a misfire under load in 2nd and 3rd? Then id just get a recon MAF from VW, which is £70 once you hand in your old one.

    Temp sensors are a common problem too, only £25ish from VW. This could be causing the problem.

    Also, check for boost leaks http://uk-mkivs.net/forums/t/190273.aspx

    Luke

    A bit of this, a bit of that. 220.9Bhp
    Have a closer look

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    What do you mean disconnecting the MAF is a myth? It's not true that disconnecting the MAF has an affect on driving performance? I disagree. How is the ECU supposed to get a reading from a sensor that is not connected? If the sensor is non functioning for whatever reason then it will be ignored and a pre-written map will be used in it's place. This pre-written map will have no variables at all, so therfore the air/fuel ratio will be at a costant value, hense the poor performance. The only feedback the ECU has in this case is from the O2 sensor. A dodgy MAF connected can have a worse affect on driving performance than with it disconnected, "limp mode" in some cases will run better, so disconnecting the MAF can show a fault if there is one. All this is in my own experience, Skoda Octavia Vrs running 220+ bhp thanks to a jabba remap.

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    MAF disconnect, and if the car runs stronger IS EVIDENCE that the MAF is goosed.
    not a myth, a diagnostic fact.

    why?

    when connected but under reading (dying) the ecu cannot know it is under reading ad will assume the low level of metered air is all thats passing it by.. It can and will trip mil codes for adaption limit exceed on lambda as it tried to correct a situation of MAF saying 100g/s was being drawn in, when in reality 150g/s was, so short fueling lean by some 50g/s, which lambda tries to correct but cannot when the gaps is too large.

    when disconnected ecu has to run on the other tables, which generally runs richer, so when performance seems to be better for a disconnected MAF its 99% certain the one in there is poorly.

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    i have disconnected my maf wen the car is runnin and it splutters then dies but will start again i took it for a drive and no difference. what should i do????

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    If you suspect that the MAF is the source of the problems you're having then see if you can temporarily swap one with a friend, this should confirm that it's faulty. The next step then is to buy a new one, not cheap but it's got to be done if you want you're car running right. The MAF can be cleaned but how long it will be until it fails again.........who knows, only sure fire way to resolve your prob's is to replace with new. As mentioned before though, the temp sensors can cause similar running issues, and you mention that the temp gauge is not reaching it's normal reading, which means that either the new one you put in is faulty, or the old one was dead or dying.

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