Hi
I've got a 1990 H Cavalier SRi which is misfiring when cold. It's almost like it's only firing on 3 cylinders (doesn't rev smoothly, jumps occasionally) for the first 10 minutes but then very definitely clears up in an instant and runs fine.
It has only been behaving like this since I topped up the oil, so I could well have knocked something when I did that. I've had a good look about and can't see anything obvious; any ideas? What could cause it to go from lumpy and rough to normal in a second?
Cheers for any help,
Mark