Rough engine after jump start

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  1. Rough engine after jump start 
    #1
    Bimmer Fan
    Car Details
    neildp's Car Details
    Model of Car:
    318i SE
    Year of Manufacture:
    2000
    Transmission Type:
    Manual
    Car Body Type:
    Saloon

    Join Date
    May 2013
    Location
    England
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    Hi

    About a week ago I jump started my old 318i from my new one, (new one is a manual 2000 plate), and the new one is now running rough. I definately didn't cross the leads, but didn't realise there were terminals under the bonnet, so jumped it straight from the boot. In the rush I was in I also can't clearly remember if I made all connections in the proper order, (ie. positive on first, off last - which is now ingrained in my brain)..

    Basically I got it about 6 weeks ago, and after putting it through for a service it was perfectly smooth and perky. Now it is rough and lumpy. It still picks up speed as you hold down the pedal but the spring isn't there and it's more like bus than bmw.

    The check light for the rear lights also came on but the lights are working. It went off, came back on and is now off again. Hopefully this has corrected itself, but I'm less optimistic about the way it is driving. Everything else seems okay, although the idle speed does seem a fraction high or is taking a bit longer to settle. It's still under 1000rpm and does find it's way back to 750 but it's making me paranoid.

    Does anyone have some ideas on what sort of damage this is a sign of, either by not using the bonnet terminals, or by connecting negative first/disconnecting last?

    The old car has now gone to webuyanycar, so I don't know if that one was affected in any way.

    Thanks

     
     

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    #2
    BMW Crazed
    Car Details
    P_Monty's Car Details
    Model of Car:
    330Ci Msport
    Year of Manufacture:
    2004
    Transmission Type:
    Manual
    Car Body Type:
    Convertible

    Join Date
    May 2012
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    wiltshire
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    I'd be very surprised if you did any damage by connecting the leads directly in the boot or by connecting in the wrong order. I'm fairly sure that if you had connected them back to front, you'd know about it - major sparks and damage to the car electrics...
    Maybe I'm putting 2 and 2 together and getting 6, but is your alternator OK? My logic is if you had to jump it in the first place then the battery wasn't properly charged and a friend of mine had something similar - his 330 had a duff alternator - when we jumped it off mine it ran fine (ie still connected to my car), but soon as we disconnected the leads it ran like a bag of nails - I'm guessing the battery volts weren't enough to run the ECU correctly or something similar.
     
     

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    #3
    Bimmer Fan
    Car Details
    neildp's Car Details
    Model of Car:
    318i SE
    Year of Manufacture:
    2000
    Transmission Type:
    Manual
    Car Body Type:
    Saloon

    Join Date
    May 2013
    Location
    England
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    2
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    Hi

    Thanks for your reply. The car with the dead battery was my old one though. I just had to jump start it from my new one so I could get it moved. The old one has now been scrapped. The new one is the one I'm worried about, and was perfectly smooth like it's meant to be before the jump but is now running rough, (like a bag of nails). I'm thinking there could have been a power spike to the new one as everything was fine before this and the symptoms started straight after. The way it is running sounds pretty similar to what you say though, so could the good alternator have been damaged and now be low on power to the ECU? The rough engine must be the cause of something electrical as the jump was the only thing in between it running fine and like a tractor.
     
     

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    #4
    BMW Crazed
    Car Details
    P_Monty's Car Details
    Model of Car:
    330Ci Msport
    Year of Manufacture:
    2004
    Transmission Type:
    Manual
    Car Body Type:
    Convertible

    Join Date
    May 2012
    Location
    wiltshire
    Posts
    183
    Images
    3
    Thanks
    16
    Thanked 10 Times in 10 Posts
    I guess its possible, but I would have thought it wasn't very likely that the jump-start damaged something..
     
     

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