My baja has the xcelorin 8750kV combo and recommended servo. I'm using a different receiver but it works fine. I went to use my micro today, the steering works but the brushless motor was twitchy, just sit there and twitch. I don't know what happened. The battery is charged too. Any help would be appreciated.

Try a different battery. I know my mamba will do the same thing if the voltage is too low.

I'm using the 2 cell losi lipo. I tried the stock NiMH battery earlier today, it didn't really have enough power but it was still twitchy. It was working fine with the lipo then I turned it on the next day and it's doing this.

teamcrf, does your speed control have a lipo setting?

If so and it is set on, that is what should happen, to protect the lipo battery from being damaged by getting it voltage to low, the low voltage shutoff allows the steering to continue to work but shutdown the drive the motor to protect the lipo from being discharged below approximately 6vdc.

I have seen pan cars with the speed control set to lipo and the motor will not run at all with a freshly charged 4 cell sub C pack.

I have it set to lipo. I also set it to NiMH and used the NiMH battery and it does the same thing.

Check that the solder joints are intact and that the batteries are good because: with my 1/18 and 60A ESC it starts twitching the motor back and forth sometimes with a standard NiMH battery, but not with an oversized one which has bigger wires and higher discharge capacity. The theory this gave me is that the ESC freaks out by too large of a voltage dip, and it only happens when I give it full throttle.

The other possibility: does the motor almost sound like it's beeping? Because if so, maybe it is(beeping) and you should check your throttle trim. All brushless systems I've looked at have a launch throttle safety circuit.