2012 Yaris 1.33

[Kelton]

My 2012 Yaris in automatic mode, the engine roars away when going down steep inclines. Seems as though it's failing to adjust for the change in descent.

Anyone else noticed this?

[MikeSh]

Sounds like it's using engine braking - which would be correct operation.

[Cyker]

Overrevving an engine from engine braking is as bad for it as overevving it normally; That said, what sort of speed are we talking about here?

[Kelton]

varyning speeds but 30/40 mph a good example, over revving doesn't stop until you break down to around 20mph (annoying drivers behind) or bottom of incline is reached

[Cyker]

Hmm, I don't really know... I don't have enough experience with autos to know whether that's normal, but I don't recall ever having an auto downshift on me when I've been rolling down a hill!

[MikeSh]

Hmm, I don't really know... I don't have enough experience with autos to know whether that's normal, but I don't recall ever having an auto downshift on me when I've been rolling down a hill!

It varies a lot. Some will downshift a bit if you are accelerating with no throttle, but in my experience it's more often linked to the brakes. If you are going down steep inclines as the OP says then you are probably holding the car back with brakes and after a few seconds the auto controller detects this and 'helps' by changing down - just as a driver of a manual car might/should do. That said the MMTs we've got currently don't seem to do that, I have to use the M function on a regular steep hill, but the new CVT might well do it as it doesn't involve a possibly jerky downshift. Probably a case of reading the handbook to find out.

Incidentally the OP said the engine roars away, not that it's overrevving. Most engines (in small cars) make quite a din long before redlining.

[Cyker]

Actually he does in #4 :)

But this is just semantics; We both understand what the OP means, i.e. that the engine revs are climbing more than is comfortable when he's coasting down hill in-gear.

I would certainly never let my D4D go above 2500rpm when rolling down a hill; I'd shift up and use the brakes more! (Or the aircon! ) Of course, you don't have that option in automatic mode which is where the problem lies here. Short of flicking it to manual mode (Assuming the CVT has such a thing) I'm not sure what you can do about it.

What RPM does the engine hit? 3000rpm would be likely for a petrol and would sound pretty nasty but as it's a japanese engine it'd not likely to cause any long term damage. If we're talking closer to 6000rpm then... yeah... that is not good!

[Lustral]

I have a 2012 SR CVT Auto , when im in the usual D position and there is a massive down hill , i just downshift manually using the paddleshift , this will temporarly drop down a gear to help engine breaking and the RPM goes to almost 3K RPM , but the car doesnt gain any more speed, this is usually about 30 mph downhills i have to tackle.

3K RPM does sound a little noisy esp when doing 30 MPH , but if is more than that i would say there is something wrong with your auto, but you can usually feel the car holding back enough if you just paddleshift down a gear