Two problems related to emission control have been reported for the 1999 Toyota Sienna. The most recently reported issues are listed below.
My van had first engine oil sludge problem at 32782 miles in March 2003. Finally Toyota paid the repair cost after many phone calls. One year later, on July 5,2004, I found that there is no engine oil left again during the middle of our family vacation trip (at 46000 miles). And blue smoke comes out from exhaust pipe again. Toyota couldn't fix the problem by clearing changing some parts. I request Toyota replace the defect engine.
Engine light appeared. Oxegen sensor fried 5 times.