2001 Toyota Sienna AC stops at idle.

All in the link. also click on the images tab.

https://www.google.com/search?q=22re+engine+ecm+wiring+diagram

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You have an engine cylinder misfiring, run a fault code test with a scanner to see what cylinder is misfiring. Misfire codes look like this P0301 is cylinder number (last digit of fault code) one and so on.

probably low on freon

this happens to me a bit when the weather changes or rains i just floor it and take off u have to get going quickly told my mechanic but it started for him no problem if i make short trips after starting out it stalls on me so i leave it running when i run into store or bank works for me

I would change the transmission filter.if clogged it will slip and loose power on steep upgrades try that it is inexpensive. If that don't help you may need a new transmission.

Yes could be... also the engine should only idle at about 600 when warmed up and 1200 on cold start up so get it checked out a any good garage...

Maybe the MAF. (Mass air flow sensor)

the idle air control motor is failing

the crank position sensor and map sensor is malfunctioning

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.