I was in the mountains fishing when I went up a steep highway with 15% grade for a few miles when the car began bucking and losing power intermittently. The car would buck, lose power briefly and then it would come back on and go another 30 seconds or so and do it again. I was running about 35 mph at the time. As soon as the car topped the hill, everything went back to normal for the 250 mile trip home. No codes or other symptoms. Never heard of anything like it.