Hello guys ive been having more problems with my t-maxx 2.5... When i lift it of the ground the wheels are like stuck and won't go forward but when i put it down the wheels go? It seems like it is not engaging because sometimes the wheels will like "catch" and will start to turn. What is wrong here?

Also ive been having problems with it not running right in the winter. Do nitro engines need to be warm? i put tin foil around the head of it and i think it might help but it still doesn't have much power and doesn't like to run right. When i give it gas it likes to stutter then shut off? Or when i get it warmed up it still likes to not run well when i give it a lot of gas or just a little sometimes.. What should i do?

Thanks for the help