My 2000 Sienna jerks while in drive and suddenly comes to a stop while the engine is still running. What might be the problem?

SOURCE: 2000 sienna stalls, loses power and engine sounds

After about 100K + miles the idle air control valve (IAC) begins to collect carbon deposits that interfere with the movement of the spring-loaded valve. You will not be able to clean this without removal and dissembly of the IAC body. Use an emory cloth or fine sandpaper to remove the build up around the valve. This should free it up to rotate without binding. This is a temporary fix, of course, and will either require cleaning again or replacement of the valve. Getting to the IAC requires removal of most of the intake upto, but not including, the intake manifold. Total time is approximately 3-4 hours, but worth it. Good luck, and I hope this helps.