Hi my fiance has a 2000 Honda Odyssey and just a week ago I bought a CV Axle for the front left which needed replaced. Installed it without snapping the axle in place so when I went to drive it, it would Rev up but not go. Jacked the van up and made sure it snapped in place. It was fine. Now sometimes when at a stop and try to accelerate the rpmS go up bit van doesnt go right away. When I was driving on the highway with my cruise control on it would randomly accelerate making the rpms shoot up so I just turned the control off and drove myself. WHAT COULD IT BE....

 

Sounds like something in the transmission - possibly a shift solenoid? I'm sure a more informed expert can weigh-in more accurately but you might try testing those...