is it the HPI MT2 RTR?
If so the .15 it comes with is Junk, my Brother-in-law has gone through 4 engines already, all under warranty from HPI. the engine that comes in that is junk, his does the same thing yours does. I just start the tune all over again, reset the needles etc. but if he hits a hard jump, runs out of gas or goes through more than 3 tanks the tune goes away again.
we just went with a O.S .18 CR-V worked fine from there