Is There A Fix For Auto Trans Wont Shift Into 4th Until Warm?

[Astroman]

Wow two pages and no correct answer why the transmission is locked out of 4th. It has to do with emissions (the cats need to be at operating temperature to work properly) and the quickest way to get them up to temp is by running the engine at a higher RPM. If your not going over 45mph why are you so worried about not getting into 4th for that short of a commute? My car only takes a mile at 30mph to get up to operating temperature, even when we were in single digits. Stop and go, tires, conditions, winter gas and other habits have more effect than not being able to get into 4th at 45mph.

[bronsin]

Originally Posted by Astroman

Wow two pages and no correct answer why the transmission is locked out of 4th. It has to do with emissions (the cats need to be at operating temperature to work properly) and the quickest way to get them up to temp is by running the engine at a higher RPM. If your not going over 45mph why are you so worried about not getting into 4th for that short of a commute? My car only takes a mile at 30mph to get up to operating temperature, even when we were in single digits. Stop and go, tires, conditions, winter gas and other habits have more effect than not being able to get into 4th at 45mph.

True probably that last part. But also it just bugs me the transmission will not shift into high gear sooner. How much better mpg would it get? Only one way to find out. Remember if it takes a mile to warm up and youre only driving six miles thats a pretty large fraction. I think putting a hot plate under the block for half and hour at 700 watts (about 7 cents at my rates for that time of day) might be more cost effective though.
Wait a minute...thats already patented isnt it? Dont they call that a plug in hybrid?

[sbergman27]

Originally Posted by Astroman

Wow two pages and no correct answer why the transmission is locked out of 4th.

In fact, I've mentioned emissions as a possibility. However, with all due respect, without a reference, your assertion is just another hearsay post.

As I've said before, given the same power requirements of the driver, there is no fundamental reason to think that the engine would warm up any faster at high rpm/low torque than at low rpm/high torque. Same goes for the catalytic converter. In the latter case, more air-fuel is packed into each cylinder, but the total amount of air-fuel/sec (and exhaust gas) is going to be about the same.

There may be other effects that make the higher rpm scenario advantageous. But I don't see any fundamental reason that it would be.

-Steve

[41magmag41]

I checked gas mileage yesterday morning with my scan gauge during the warm up run to work. It was 31 degrees out. With the transmission lock out until warm up at 40 mph in third gear the scan gauge read 32 mpg the entire time before the car reached 137 degrees and it kicked into fourth. I don't consider that lousy gas mileage.

I think all this yaking about overriding the computer to get better gas mileage for a couple of minutes will do more harm than good. I've just offered proof that the car still gets decent mileage when it's in the warm up mode before 4th gear is available. Why not leave well enough along. My girl has 98000 miles on her and I average 38 to 41 mpg year round when averaged together. I don't baby her in the interstate, run 75 to 80, and still get good economy.

Much to do about nothing other than to hear yourselves talk. Have a good day.

[bronsin]

Originally Posted by 41magmag41

I checked gas mileage yesterday morning with my scan gauge during the warm up run to work. It was 31 degrees out. With the transmission lock out until warm up at 40 mph in third gear the scan gauge read 32 mpg the entire time before the car reached 137 degrees and it kicked into fourth. I don't consider that lousy gas mileage.

I think all this yaking about overriding the computer to get better gas mileage for a couple of minutes will do more harm than good. I've just offered proof that the car still gets decent mileage when it's in the warm up mode before 4th gear is available. Why not leave well enough along. My girl has 98000 miles on her and I average 38 to 41 mpg year round when averaged together. I don't baby her in the interstate, run 75 to 80, and still get good economy.

Much to do about nothing other than to hear yourselves talk. Have a good day.

You may be right but I dont trust any scan gauge. I have an instant mpg readout on my motorcycle. Before it says the engine is at operating temp it reads like 20 mpg. Thats in fifth cause it shifts when "I" want it to. It reads 40 mpg when warm. Actual mpg in winter covering the same distance is ~30 mpg. The idle rpm is 3000 until warm also. Another government/manufacturer intrusion into my life... I will adjust that this summer though. And perhaps a hotplate warmup is in order next winter...

[Astroman]

However, with all due respect, without a reference, your assertion is just another hearsay post.

I don't post hearsay, but heres your reference: http://www.yarisworld.com/forums/showthread.php?t=1579

It's in the owners manual

[41magmag41]

Originally Posted by bronsin

You may be right but I dont trust any scan gauge. I have an instant mpg readout on my motorcycle. Before it says the engine is at operating temp it reads like 20 mpg. Thats in fifth cause it shifts when "I" want it to. It reads 40 mpg when warm. Actual mpg in winter covering the same distance is ~30 mpg. The idle rpm is 3000 until warm also. Another government/manufacturer intrusion into my life... I will adjust that this summer though. And perhaps a hotplate warmup is in order next winter...

what an "engineer" that doesn't trust insturments?

[bronsin]

Well...send me one and I will try it out. And report my findings.