I have a 2008 Taurus. I am very happy with my car, and it has over 200k miles, but I have had a small problem with it for a while now. I did not change the spark plugs until about 120k miles. At that time, when I was driving uphill on the highway and before the transmission downshifts, I would sometimes get a skip/misfire (sort of the car bucks) in the engine. I found that if I put super unleaded gas in the car then it happens much less frequently. Maybe I waited too long to change the spark plugs and did some other small damage to the car to cause this. It continues even after changing the spark plugs.
When I tell the dealership, they don't really know what to say and they suggest fuel system cleaner. That doesn't help.
I found this link online and this seems to be exactly what I am seeing:
Engine Buck/Misfire at Freeway Speeds : Ford Taurus Engine
Has anyone had this happen to them? Does this sound right? Is this a big repair?
Any input on this is appreciated.