2020 4runner shifting issues

It will be in there most of the time if the dealer entered the information correctly. Just pulled up mine and everything on the Carfax was in the Toyota service history with a bit more detail.

 

I'm posting here so that if somebody is looking for information about weird downshifting when coasting downhill (2016MY and newer) I was given a master diagnostic technicians explanation plus a bunch of paperwork.

The government no longer wants our cars to get good MPG. That is a fact based on tailpipe emissions standards. They are now aggressively going after tailpipe emissions. So, when you're coasting down the hill your engine would still be putting out the exhaust of a car running at a higher speed, still not as much as if you're just coasting, but that doesn't matter. So, our government overlords and tyrannical leaders who have used science by consensus (science cannot be voted on, but try to tell them that) decided that the cars should downshift when coasting so that the engine puts out less emissions. Screw the citizens who are paying politically decided ultra high gas prices.

I drove the same hill on two different 4Runners and the first time I switched to manual shift to see that I was in third gear.

My 2020 OR allowed me to manually shift into fourth, but after a little while it took me back to 3rd.

My 2023 ORP allowed me to shift to fourth and it remained there. If there was no other traffic, I would have pushed it up to 5th to see what happened.

I can say that my mileage shot way up, on the entire trip it was easily 15% better just manually shifting to fourth in the first 8 miles of a 35-mile trip. Hopefully, I'll remember to try fifth next time.

@duc_minh206 also observed a difference between the 2020 and 2021 models, so I guess we could deductively reason that there may have been a reprogram on 2021 models.

 

I read this 4 times and still am having a hard time understanding what you mean. Do you mind elaborating on your logic please?

 

Think of it this way...

You can idle at 1700 RPM or you could idle at 1200 RPM. When you're coasting it's kind of like an idle since there's really not a load on the car.

So say you're coasting at 60 MPH. Ultimately, the engine is running with the transmission and those pistons are still firing off matched to the RPM. The programmed downshifting lowers that RPM, lowers the number of times those cylinders fire thus lowering emissions out of the tailpipe and lowering your speed while you are trying to coast.

While the engine doesn't slow down per se, coasting takes the load off of the engine and that's where your fuel trim adjustments take care of themselves, less fuel to get the same RPM.

Does that work?

 

The exact opposite is true.

 

Time to call Toyota engineering and the EPA.

PS I will elaborate, to make sure context is thrown out there...

Sure, initially the lower gear will make the engine run at a higher RPM. Great for 2,000 feet but, the engine braking will have a long-term effect over 10,000 feet, etc. Some of the documentation on screen that I looked at at the dealership even had graphs of what the intended effect was.