Toyota RAV4 Forums banner

1 - 8 of 8 Posts

·
Registered
Joined
·
264 Posts
Discussion Starter #1
We've got 2000 miles on the 2014 XLE fwd now and I've noticed a sensation while braking to a stop that has happened enough times that it's not a fluke. In certain conditions of de-acceleration and possibly the slope of the road somewhere between 15-25 mph the rate of slowing lessens noticably and I have to apply a bit more pressure to the brake pedal to get back to the same stopping rate. It feels like maybe the RAV is downshifting and giving a bit of throttle but it gives a little bit too much and it feels like a push or that you let off the brake slightly. It doesn't happen on every braking to a stop situation so I've been unable to define exact speed, rpms, etc. Anyone else notice this?
 

·
Your Humble Administrator
2008 RAV4 Limited V6
Joined
·
16,639 Posts
We've got 2000 miles on the 2014 XLE fwd now and I've noticed a sensation while braking to a stop that has happened enough times that it's not a fluke. In certain conditions of de-acceleration and possibly the slope of the road somewhere between 15-25 mph the rate of slowing lessens noticably and I have to apply a bit more pressure to the brake pedal to get back to the same stopping rate. It feels like maybe the RAV is downshifting and giving a bit of throttle but it gives a little bit too much and it feels like a push or that you let off the brake slightly. It doesn't happen on every braking to a stop situation so I've been unable to define exact speed, rpms, etc. Anyone else notice this?
Above a certain speed, the transmission's torque converter locks up to prevent slippage and therefore save fuel. What you're feeling is the torque converter unlocking, so you get less engine braking. It is a weird sensation, but you'll get used to it.
 

·
Registered
Joined
·
627 Posts
Anyone else notice this?
Yes, and it happens to a certain degree to all modern fuel-injected vehicles, although is it more noticeable in some Toyota models, to the point of some people complaining to the NHTSA. The "bigger" the engine in relation to the weight of the vehicle, the more pronounced the effect. The FJ Cruiser is probably the worst offender with some people even claiming that they can feel their vehicle accelerate.

Here is what happens, in addition to what JuneBug said. When the vehicle is coasting or decelerating above certain speed (typically around 25 mph but varies from model to model), the ECU cuts off fuel completely to maximize fuel efficiency / engine braking. When the speed and rpms fall below a predetermined limit, the ECU starts sending fuel to the engine again, at idle-level. The combined effect of fuel being sent to the engine and torque converter unlocking reduces engine braking effect, and feels as if the vehicle is not longer braking that effectively.

You can actually catch it happen if you look at the instantaneous fuel consumption "bar" on the car entertainment display. You will notice that when decelerating / braking, instantaneous fuel consumption is "99.9 mpg", which means that fuel has been completely cut off. When the speed drops to a certain value, you will see the fuel consumption spring up to something like 60 mpg, and then gradually decrease to 0 when the vehicle stops.
 

·
Registered
Joined
·
641 Posts
You can actually catch it happen if you look at the instantaneous fuel consumption "bar" on the car entertainment display. You will notice that when decelerating / braking, instantaneous fuel consumption is "99.9 mpg", which means that fuel has been completely cut off. When the speed drops to a certain value, you will see the fuel consumption spring up to something like 60 mpg, and then gradually decrease to 0 when the vehicle stops.
I was observing this behavior but was missing the part where idling fuel is being injected by the ECU after the speed drops below that certain threshold. The second part of this paragraph is the light-bulb moment.:thumbs_up:

Thanks and good luck with the new Venza. I'll missed your insightful & technical replies.
 

·
Registered
Joined
·
627 Posts
I was observing this behavior but was missing the part where idling fuel is being injected by the ECU after the speed drops below that certain threshold. The second part of this paragraph is the light-bulb moment.
It was very noticeable in my FJ Cruiser with manual transmission. The transition would occur at ~1000 rpm.
 

·
Registered
Joined
·
264 Posts
Discussion Starter #7
Thanks for the explanations, it's exactly what's happening. Funny it isn't noticed every time the RAV comes to a stop.
 

·
Registered
2020 Rav4 LE
Joined
·
4 Posts
So this is a common issue with Toyota, its surprisingly that it occurred even on the old models how come Toyota did not do anything about it, I recently got Rav4 2020 LE AWD and feel the same way when I applied brake to stop on the stop sign, when I press the brake pedal the car accelerate a little for 2 seconds and started to slow down, its scary that it feels you going to hit the car in front of you.
 
1 - 8 of 8 Posts
Top