I'm not to sure about the engine, but with the steering I might be able to help. Take the servo off and see if you can easily turn the wheels by them selves, if not, dis assemble the whole assembly and check for any broken/bent pieces. If it all works fine check the servo, turn the servo horn left to right to see if it is smooth or not, then do it with the radio. If you find that the radio doesn't make it turn or the servo is weak I might suggest getting a new servo (Preff metal geared) or you could take it to your LHS and they prob could fix it for you (I can't see/feel it, hence why it's hard to diagnose.