[George]

I have A170CDI year 2000. In damp/wet conditions car seems to missfire and jumps like a kangaroo, in dry conditions perfectly fine. Has anyone came across this before and if so any suggestions. Thanks.

 

[CharleyNokia]

Maybe you're getting water spalshing up onto your coil pack unit. With your bonnet open, looking downwards, behind the radiator, there should be a plastic cover with some cabling loom to your right(left of car) This black cover, if you have it, covers the ignition coil pack. If it's missing, the protection is gone.