One problem related to fuel injection has been reported for the 2004 Toyota Sienna. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Toyota Sienna based on all problems reported for the 2004 Sienna.
Sienna le, bought in may 2003. Gas pedal lull!!! when coming to a rolling stop and then have to accelerate, the gas pedal has a lull so you push a little more and you screech the tires. This has almost caused two accidents, cutting across traffic, someone was letting me go and the hesitation gave the apperance that I was not going so he started to proceed and finally it kicked in and he almost side rear ended. It also seems to be more pronounced in wet road conditions, can't wait for snow! brought back to dealer and says it is completely normal, gas pedal is controlled by computer can not change it!.