OK so this sounds very familiar to the problem I have been having. I have a Dodge Journey R/T 2010 with 44,000 KM's on it. When I took it into the dealership they said engine was misfiring and the problem was in cylinder 5, they changed the spark plugs, coil,did the leak test and a carbon cleanse cause they said I had carbon build up. I questioned how that could be in a brand new vehicle and he blamed the gas I was using. I told him I use the gas the manufacturer specs indicate and he had no answer. We won't go into the Customer Service issues I have with this particular dealership, but as soon as I left the dealership, I have the same problem. Because I did not have confidence in the dealerships ability to take my concerns serious, I took it to another dealership and sent 2 letters to Chrysler Canada so far.
I just got a call from the other dealership, claiming that they are getting the same reading and that the engine was still misfiring and that the problem was still in cylinder 5, but that now they were taking it apart to clean manually because there is carbon build up. Of course I questioned how that can be and the fact that there has to be some other under lying reason.
BTW my engine also revs up when you put it on cruise control, which they answered and said they changed the computer program. WHAT?
Anyway, did any of you ever figure out what the cause of the issue was?