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.