My truck has recently started surging frequently, most frequently while taking off from a stop. It will sometimes do it at other times as well when accelerating or at a change in grade at low speed. It will take off, then stop, and then continue doing surging until I let completely off the throttle. It will sometimes die while doing this. The only thing I have done to it recently is replace the U joints, and I don't see how this could be the cause. The throttle position sensor has been replaced, but not recently. It is showing no codes and after I get it going, everything seems fine. Any ideas?