westport44

owns a4 1.8 petrol 1997, had running problems ,stalled when cold,change d plugs,leads no improvement ,mislaid ignition key used spare key it ran perfectly with new key.I looked at the plugs again they were very black (coked up).checked engine oil found what i think is petrol in oil.I changed the oil drove about 25 miles the oil level is rising. Iwould appreciate if any members could give me any clues to the problem. it has being a wonderful motor. your help appreciated thank you westport44