Toyota Sienna Forum - siennachat.com banner

Loss of power at steep downhill exits.

3K views 29 replies 12 participants last post by  20swrt 
#1 ·
Anyone else lose power when exiting a steep driveway or ramp? It has happened 4x in nearly 10k miles on our 2021 XSE.

All times while exiting a business or driveway with a steep exit trying to accelerate into traffic and I have zero power for a few seconds. Almost as if the safety sense thinks the ground is an object.

I’m bringing it in just to document it as it’s a huge issue sitting dead in the water when trying to merge into traffic
 
#4 ·
I have had several hybrids (Sienna has not yet arrived), 2 Toyotas, 2 Hondas, and all of them would charge the battery when going downhill. I dont think you have a need for power when coasting downhill, mostly. Key word "when going downhill". Your car is slowing down on exits, charging the battery. My opinion is dont worry about it, the hybrid system is great, but not perfect.
 
#8 ·
sorry for any confusion. The condition I’m describing is not coasting downhill doing regen. It’s from a stop

Imagine you are exiting a business that isa few feet higher than street level. From a complete stop, and your van is pointed downhill or down the ramp, as you prepare to merge by releasing your brake to get over the line and you hit the gas there is zero power. It’s like you’re coasting in Neutral for 2-3 seconds. Then power slowly comes on. Similar to starting a manual transmission vehicle in 2nd gear.
 
#5 ·
Not sure if the Sienna does it, but the Gen 2 & 3 Prius had a transaxle protection on loss of traction. It would cut power when you slipped even a little bit to keep the electric motors from applying too much torque. Are you stomping on the gas when this happens? Also FWD or AWD?
 
#7 ·
I’ve driven a Prius for a few years and never experienced it.

How it always happens is I let my foot off the brake as I prepare to merge and when I hit the gas there’s no power for 2-3 seconds when my foot is flat on the gas.

I usually don’t accelerate downhill as it has no front clearance. I wait until the vehicle is relatively flat. I have a AWD
 
#12 ·
Only had happen once and not even sure it was same as being discussed.

Was in PA and just stopped for gas. The station was lower then the road around it and the road was a bit lower then where the edge of the gas station meets the road. So like going uphill and then a bit downhill.

Was turning left onto road when lost power for a split second. Not sure if it was having the rear tires lower relative to the front tires plus turning. No wheel spin and no alerts on MID.
 
#14 ·
Do you have an AWD by chance?

It happens sometimes during a reverse too when backing out of my driveway, switch to drive, and nothing until the engine kicks in. Happened twice this Summer as I remember having AC on full blast and thought it could be an issue.
 
#17 ·
Happend to me at leat 5 times when pulling out of the same driveway. Right hand turn. Driveway is flat. No curbs, potholes etc to trigger traction/abs.
Ice engie is usually off when it happens so it try to pull on electric only.
Last about 3-7 seconds. It just crowls forward almost totall loss of power.
Last time when it happend i floored it without any effects, after rougly 6 seconds ICE kicked in and it started moving but at this point i had a car right at my tail. It is definietelly quite dangerous. I lost confidence when making turns or pulling out of diveways.
 
#19 ·
False positives from the front radar or sonor senors when they see/detect the road itself as an object. The scrape marks carved into the road in the pictures in post #9 are a BIG clue as to steepness of the intersection.

Our house driveway has a fairly large angle of attack like those above. My nissan with RCTA "slams on" the brakes when reversing out too quickly (slowly doesn't activate it) yet our Sienna rarely activates on it.
 
#27 ·
@DadWagon: Did you ever get to the bottom of it?

I have never had this problem. The lane assist is surely overprotective, as it keeps buzzing all the time on narrower roads. When on ACC the van might slow down if it detects something that, in its opinion, is too close, but not when you operate the gas pedal yourself.
 
Top