This problem started after 1 year of ownership. We would experience about 1 to 5 times per week. It gets very scary as the van would unexpectedly slows down when you accelerate and the car behind you would almost run into you. I guess the worst case would be when you need to make a left turn and you need to clear the oncoming traffic and your van slows down.

I HOPE TOYOTA is listening to this!!! I am very glad I found this website!!! Starting at 15K miles service at Irvine Toyota, we have been complaining to dealer in vain. Do something before anything happens. You GOT a big lawsuit coming from Sienna owners if you don't fix this...

VEHICLE SEEMS TO LOSE POWER WHILE TRYING TO ACCELERATE. THIS DOES NOT HAPPEN EVERY TIME BUT ONCE IS ENOUGH TO SCARE YOU.THIS SEEMS TO HAPPEN AFTER TAKING FOOT OFF OF GAS PEDAL THEN TRYING TO ACCELERATE.SOMETIMES WHILE MAKING A TURN , SOMETIMES WHILE JUST CRUISING ALONG BUT THE SCARY PART IS WHILE ATTEMPTING TO GET ON THE HIGHWAY.THIS CREATES A VERY DANGEROUS SITUATION.THE VEHICLE DOES NOT STALL BUT JUST SEEMS TO LOSE POWER FOR A FEW SECONDS.TOYOTA DEALER RAN A DIAGNOSTIC TEST WITH NEGATIVE RESULTS AND TOLD ME TO BRING IT BACK AND LEAVE IT FOR THE DAY. ANY OTHER SIMILAR SITUATIONS OUT THERE Just cut and pasted this from Dennis who had the same problem. My van is doing this while turning and merging into traffic.

Tony

VEHICLE SEEMS TO LOSE POWER WHILE TRYING TO ACCELERATE. THIS DOES NOT HAPPEN EVERY TIME BUT ONCE IS ENOUGH TO SCARE YOU.THIS SEEMS TO HAPPEN AFTER TAKING FOOT OFF OF GAS PEDAL THEN TRYING TO ACCELERATE.SOMETIMES WHILE MAKING A TURN , SOMETIMES WHILE JUST CRUISING ALONG BUT THE SCARY PART IS WHILE ATTEMPTING TO GET ON THE HIGHWAY.THIS CREATES A VERY DANGEROUS SITUATION.THE VEHICLE DOES NOT STALL BUT JUST SEEMS TO LOSE POWER FOR A FEW SECONDS.TOYOTA DEALER RAN A DIAGNOSTIC TEST WITH NEGATIVE RESULTS AND TOLD ME TO BRING IT BACK AND LEAVE IT FOR THE DAY. ANY OTHER SIMILAR SITUATIONS OUT THERE . THANKS