We had a similar problem just days after purchasing the van. Ours was a cylinder 6 misfire. The dealer went through the same steps as yours over about 4 weeks but fixed nothing. The dealer ended up working with Chrysler s/w engineers and finally fixed it with a software update. Something to look into, maybe.Posting this here in case it helps anyone else out. But I also want to check whether I was ripped off. We have an extended warranty but are required to take the car to our non-preferred mechanic.
Our CEL came on with the P0305 code that cylinder 5 was misfiring. The mechanic wanted to change out two bad ignition coils and replace all spark plugs. In addition they recommended a fuel induction service to clean out the engine. I figured at 74,000 miles that wouldn't be a bad idea. Here was the cost:
Ignition coils - Parts $170, Labor $319
Spark plugs - Parts $155.94, Labor $145
Fuel Induction service - Parts - $90 (fuel system cleaner), Labor $99
Total parts and labor was $1337. Thankfully warranty covered $471 of it. But that seems awfully high.