I have been fighting this problem for a year now and I can't find a good honest mechanic where I live. So what happens is that when the temperature outside gets into the 40's or below my jeep won't go when it's in drive. It only does it when the engine is also cold. I'll have it in drive and hit the gas peddle and the jeep bogs down. It will make a loud pop then starts to go a little before doing it again. The pop sounds like it's coming from the headers. Once the engine in the jeep gets to the normal operating temp it works fine. The colder it is the worse the problem gets so any help would be very welcome and appreciated.