In a word 'tracking' often caused by moisture getting in the distributor cap on on the H.T.leads casuing the high voltage to track/short out and therefore causing the spark plugs to misfire.
Checked out all electrics and renewed as much as I can but symptoms persist....only in the damp. It`s as if an automatic choke is starving the engine of fuel...to the point that on a few occasions it has totally cut out. strange that it only ever happens when damp.
it is possible that the damp air is mixing with less than perfect fuel in a less than perfect engine creating a bad result. otherwise, check your air filter. the thicker cold damp air is harder to suck through. finally if youre worried about the choke. if youre car is carbed, pop off the air filter and check it.