In the 1966 "Coupe des Alpes" Carlsson drove an almost-competitive car, a Saab Sonett II. The two-stroke engine had been bored to 940 cc compared to the 841 of the standard model and it gave at most . The final drive was geared down so the top speed was only , but could be reached from standstill in eight seconds. The car was capable of holding station with the Porsche 904. But they ran into problems with the spark plugs. Frequent spark plug changes were not unusual for tuned two-stroke engines, but it used up spark plugs at an unusual rate and soon they had run out of spare spark plugs and had to give up. Sabotage was suspected and the gasoline was sent to Saab for analysis, where they found that it had been contaminated with a foreign substance.