I just bought a Hobbywing Brushless kit for my Exceed Sunfire.  

I got the B4 Kit:   http://www.nitrorcx.com/ezrun-brushless-system-combo-b4.html

In the instructions,  it says to use:  With 4-6 cells NiMH/NiCd or 2 cells Lipo:   On-Road≥5.5T, Off-Road≥8.5T;

Well,  I put the motor in,  and tested it with a 7.2 V NIMH battery and the car was very jittery if you went straight to full throttle.   It would never get up to speed as it would jerk forward and then brake...  then jerk forward again continuously until i let of the throttle. 

If instead I slowly pulled the throttle back, the car would start to accelerate smoothly and then once I hit a medium speed,  I could launch into full throttle.  

I tried a few different configuration settings of the ESC,  but nothing changed the behavior really.    

I figured I would try a 3s lipo battery for kicks.   There was no jitter in the throttle.   It worked perfectly.   

The only thing I didn't try to adjust was the timing,   could this be my problem?   I'd rather be able to use my 7.2V NIMH batteries since I have a bunch of them.

Thanks!