Evo 500 engine problem (3.0 24v)

Hello Opel driver, have an EVO 500 and a problem. Who can help? In the morning when the engine is cold, the engine only takes up insufficient gas and goes off every now and then. Speed 450-500u/min I also find that the engine only runs on 4 or 5 cylinders and smells of petrol. After the engine starts again, the problems are gone. What can this be? When changing candles, an oiled candle was found in the 5th cylinder. Is this perhaps the cause?. How good are the NGK candles? Needed help because of my rear wing. Thank you to all