I had to get my engine replaced in November 2016 (the tip of a spark plug came off and damaged one of my cylinders - total fluke). After the engine replacement, the vehicle seemed fine until the weather got colder (below 30 F) I noticed the vehicle ran really rough (loud, vibrating (audible and physical), muffler noise). When it was really cold (20 F) I even heard backfiring and heat shield noises. When the car warms up, after about 15 minutes, it does run much better.

I have been at 2 different dealers, 2 different times, and I am being told this is normal operation for a Jeep Renegade. My original engine did not run like this!

Additionally, my highway mileage went from 32 to 25. The dealer says it is because I have winter tires on. I could see a 1-2 mile reduction, not 6-7 miles.

the idle of the engine changed about 2 months after i had the vehicle. there is a rough idle in the morning for about 30 seconds to a minute while the car is warming up. I was told by the service department head that Chrysler has a program fix for the issue. Well that didn't fix the problem, and my car is at the dealer again and they have had it for 2 days now, trying figure out the problem.

Update from Dec 6, 2016: So know my car has 10700 miles and still have the rough idle. I had an independent car inspector check into the issue because FCA says there is nothing wrong, but the car inspector who looked into the problem found unburned hydrocarbons in my engine coolant, BIG PROBLEM. So I will be taking the car back to the dealer and have them look at it again, but this time they will get a copy of the report I received.

Update from Jan 2, 2017: I had an independent inspection done of my car and found out some every interesting information.i cant post the report because this website only accepts pictures. To recap the high lights of the report, here they are

The day was clear skies, 53 degrees F, and 66% humidity. The check was done at the first start of the eninge for the day. it was in the morning. 1. Hydrocarbons (unburnt gas) present in engine coolant, (this was checked twice on two different days and it was found on both days) a 5 gas analyzer was used to check this. 2. Via an oscilloscope and pressure transducer, the pulse wave form of the engine idle was not consistent, it was erratic.

This being said, I'm now going back to the dealer with this report in hand and see what they say. Oh by the way the dealer I bought this car from was Nichols Dodge in Burlington NC. they have been telling me along that there is nothing wrong.