Automatic owners, rough downshifts?

[RTW YARIS]

I havent had my Yaris long, and cant complain about anything except one thing in particular. With the automatic transmission, sometimes when coasting (especially noticable on downhill/declines) the transmission likes to downshift at seemingly odd times. I notice a lot of the time it will happen while coasting downhill and I very lightly begin to tap the brake. Its almost as if as soon as I touch the pedal, the transmission will drop a gear, thinking I am slowing down or coming to a stop even though I havent slowed down much, if at all. This results in the RPM coming up a lot higher than they normally would be while driving at that speed (not so much so that its banging off the rev limiter or anything, but its noticable). Anyone else experience something like this?

[staticorex]

Yeah it's a fuel saving thing or something. Been discussed. Try searching. :)

[RTW YARIS]

pretty sure this isnt related to fuel saving. how is it saving fuel if I touch the brake and it revs to the moon?

Im not talking about the noticable "on/off" feeling you get with very light throttle input with the drive by wire system...

[punch]

well sounds like your a "know it all", so go away...

[brickhardmeat]

.................."revs to the moon"

[SmellyTofu]

Here's a "fix" if you want to coast down the hill. Flick it to N and the back into D quickly (EDIT: should read shift from D to 3 and back again quickly). It'd shift back up. It's just downshifting because obviously the automatic transmission can't read your mind and doesn't have eyes. It happens to all new electronic controlled transmission coming out. Just to help control/maintain the speed as opposed to coasting freely down a hill... more so safety related than anything else.

It is saving fuel because your engine will not use fuel to keep it running. The momentum you have going down the hill is sufficient for the engine to keep spinning at high revs without fuel. Next time you drive a car with an instantaneous fuel consumption gauge on it, try it. It'd read 0.0L/100km. (or 99.9MPG in your case).

[eTiMaGo]

read up this:

DFCO

and it should clear up a few things

[RTW YARIS]

for you slow people, keyword ROUGH downshifts.

etimago, thanks for the link. I understand the concept of DFCO, Im just curious if its doing so a little more roughly than normal. Sometimes its a pretty solid surge and not consistent so it doesnt feel right. I was curious if anyone elses was "revving to the moon" like mine.

[eTiMaGo]

Well I can't be exactly sure for the automatic, but I know in mine you can feel a bit a a jerk as the DFCO is activated.

But I think SmellyTofu is right in saying that this is just the way the auto transmission works. It's a pretty clever system but it has its limitations.

[brickhardmeat]

Originally Posted by RTW YARIS

for you slow people, keyword ROUGH downshifts.

etimago, thanks for the link. I understand the concept of DFCO, Im just curious if its doing so a little more roughly than normal. Sometimes its a pretty solid surge and not consistent so it doesnt feel right. I was curious if anyone elses was "revving to the moon" like mine.

you said ...when you touch the brake... the car..... "revs to the moon"


tee hee hee

[churp]

I manually shift down sometimes to assure DFCO kicks in....which IMO is sometimes rougher than what you're talking about (the ECU doing it). I do it manually because the ECU version requires the proper circumstances, and is a little more erratic. Try a none DFCO car....shift down with you foot off the accelerator, it will probably be rough too.

[PetersRedYaris]

What exactly doe's "to the moon" mean? Do you have an RPM gauge? Yes, it is normal for the auto to downshift on a hill if you touch the brake, but a single gear downshift hardly revs the engine to the moon. Unless yours is defective and downshifting harsher than normal, it's normal and nothing to worry about.

[SmellyTofu]

Originally Posted by eTiMaGo

read up this:

DFCO

and it should clear up a few things

I didn't read all the link, but yes, it's one thing most EFI systems use to reduce emissions. It's not a new thing. I know it's been around for decades... my old 90's Camry 3SFE engine had it but had a set rev of 1700rpm and above, it will cut the fuel line and utilise the momentum of the car whenever the throttle is closed. Uphill or downhill.

[W.A.S.P]

Originally Posted by RTW YARIS

I havent had my Yaris long, and cant complain about anything except one thing in particular. With the automatic transmission, sometimes when coasting (especially noticable on downhill/declines) the transmission likes to downshift at seemingly odd times. I notice a lot of the time it will happen while coasting downhill and I very lightly begin to tap the brake. Its almost as if as soon as I touch the pedal, the transmission will drop a gear, thinking I am slowing down or coming to a stop even though I havent slowed down much, if at all. This results in the RPM coming up a lot higher than they normally would be while driving at that speed (not so much so that its banging off the rev limiter or anything, but its noticable). Anyone else experience something like this?

Hahaha! Sorry for the "off topic" but are you a fan of Suicide Girls?

[CompanyXPaladin]

Wow.. I feel like a nub. I never knew about DFCO, and I'd like to think I'm pretty car savvy. This also makes me feel dumb for leaving my car in neutral while decelerating; it sounds like it'd actually be more fuel efficient to leave it in gear. Learn something new every day.

That said, get a manual tranny! lol

[Imagine]

I know exactly what you're talking about. The 40-50mph down shift that sometimes hits pretty hard if you take your foot off of the gas, and you can hear the engine rev pretty high on the down shift. It can be a bit annoying, and part of the reason why I hate auto transmissions.

I don't know if it's DFCO though or just really hard downshifting.