I have perfectly the same issue with m 2019 sienna LE. I also noticed that if i press the gas at neutral and it goes well above 3000rpm, on the way down it stops at 1200rpm for a second.
Solution for the vibration on 2015 Sienna at 1250RPM
There is a vibration on 2015 Sienna when engine speed at around 1250 RPM. Some vehicles are very minor, and others could be very severe. The vibration on my 2015 Sienna sometimes was very severe and along with the lower frequency drone noise. This had made me feeling very headache and ears pain. Had brought it to the dealer several times for a inspection. Nothing found! Had test another brand new 2015 Sienna SE, did the same thing, just a little better than mine. The last time I went to the dealer, they did something on the CAT converter. Before, there were four lock washer on the 4 bolts (with spring on it) those connects the CAT converter to the front and rear manifold pipe. The service tech removed those lock washers and tightened the four bolts. Because they believed that the vibration was caused by the looseness of those joins. But after I picked up my Sienna , I found the vibration was worse than before. Then I was thinking if I made it a little looser, would it be a little better?? So what I did is put 2 flat washer and 1 lock washer on each bolt. After I tightened those bolts, the spring on it will only be compressed 1 to 2 turns. I test drove my Sienna after doing this. The vibration almost went away. There is only minor vibration when cold start the car. Those drone noise also is not noticeable. If you are experiencing the vibration on your Sienna. You may try this on your car(you can put more or less washers on your bolts, just remember do not make the spring too tight, so the washer amount may vary on different vehicle). Please see the following pic for the washer size and position of CAT converter.
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Dude, what exactly do you want? If you have that drone at around 1200 RPM it has nothing to do with any sensors or fuel type. Its a crap design flaw they never caught during the design phase. My guess, most likely when they dropped the braided front pipe from previous models, probably to save a buck, is when this started, but it wont go away. So live with it or change it. There are several ways to try and cancel out the harmonic imbalance. Here is a thread that has another solution so maybe give this a try.
Engine Vibration
Hey all, With our growing family my wife and I purchased a new to us 16 Sienna XLE with 78K miles. The van is in pretty good condition and runs great. However there is an engine vibration at around 1,200 RPMs everytime it revs past it, slightly better when warm. I read a thread here about it...www.siennachat.com
At the end of the day, if you have drone its the harmonic imbalance between the engine and the exhaust creating matching sound waves bouncing off each other. Removing a bracket or adding a damper weight changes the frequencies and that is treating the cause, not the symptom.
If you have some other sort of problem not related to drone then take it to your dealer and ask them to fix it.
Dude, why do you think it has nothing to do with any sensors? Do you not think that the wrong mixture of fuel and air can make the engine vibrate?
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