2012 Patriot started jerking and hesitating, which I assume was misfire, as I approached the Eisenhower tunnel on I-70 in Colorado. Coming down the other side of the pass, it stopped doing that but of course I was not giving it gas as the hwy was downhill for several miles. Continuing on, even uphill, it was fine until it started happening again as I got near the top of Fremont pass, which is about the same altitude as the tunnel (around 11,000 feet). During several more hours of driving at lower altitudes there were no issues so I assume that it's only 11,000 feet or above that this happens. No dashboard lights, and no codes in the computer. I've driven it at those altitudes and more many times before, including Pikes Peak Hwy up to 13,000 feet last week, with no issues. With no codes, I'm not sure where to start. Ideas?