Hello, on the way from work to home have noticed that something stinks very much. Then I went down from the gas (drived there about 120) and saw in the rear-view mirror mega white cloud! I stopped and engine ruckelt very strong (smooth but not) Then I drove further and every time, where easy slope was it started to smoke again very strongly. So I drove up to home. Spark plugs I removed all (were smeared with oil and also quite old) Then all back in, engine started, each cable pulled off individually, starting with the fourth cylinder. At the fourth cylinder jerked without any difference to before, at the third the same, at the second and first engine almost went off, so clear difference) At the exhaust smelled like gasoline, then I switched to LPG and it smelled no longer like gasoline but something different. What could it be? Could it be that 2 candles have failed in a row? Please help My car: Chevrolet Captiva, 2.4 L LPG