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I had an old S10 which used a throttle cable, so I could see the linkage. For some weird reason GM designed it so when the gas pedal was 3/4 down the throttle was only 1/4 opened. Felt like a person almost had to floor it just to cruise. Who knows what voodoo happens in an electronic throttle? In the end, I fixed it with a 1/1 linkage out of a car.
You don’t need cruise control for the transmission to downshift. Can you even lug an engine with a modern automatic?
Of course not, suggested cruise control just to get the feel of it.
Would only lug if there is something wrong and the automatic transmission isn't down shifting.
My guess is Owner isn't use to the throttle.
 

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2004 Sienna CE 97k miles
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Discussion Starter · #22 ·
Actually, as I write this, I wonder if this is why some people, perhaps the OP, think their vehicle may be underpowered. You hit this "edge" of a shift, the pedal feels like it's not responding quite right because it doesn't have enough power at the low RPMs, the engine is starting to sound different from the load at low RPMs. So if they don't realize this is a transient condition that will go away if they just press the pedal a bit more to get the car to downshift, they may think the car is at the "limit" and so not press the pedal more.
I think that's what happened. I remembered giving a little more gas but saw no effect on speed (stayed at 60 mph) then I dialed back on the pedal thinking I was at the vehicle's limit and did not want to push it. The amount of extra gas I gave it usually would have taken me to 80 mph on a flat road.

MPG I calculated from a few months ago is about 23, 24 mpg combination (mostly hwy with some local).

will try to test 0 - 60 today.
 

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'04 XLE-L 2WD
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MPG I calculated from a few months ago is about 23, 24 mpg combination (mostly hwy with some local).
That's what I get too, mostly hwy with some local in the summer. In the winter it will drop to 19, 20 mpg.

My '04 is fast for me. It will easily take 7% or 8% grades on I-70 between Denver and Durango at the 65mph speed limit in the mountains and keep 80mph (75mph limit) on the shallower grades in between.
 

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2009 Sienna LE
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I think that's what happened. I remembered giving a little more gas but saw no effect on speed (stayed at 60 mph) then I dialed back on the pedal thinking I was at the vehicle's limit and did not want to push it. The amount of extra gas I gave it usually would have taken me to 80 mph on a flat road.
My 09 has the newer 3.5L engine, but I would say there are some roads I have taken that take more power to maintain 60mph on a grade than 80mph on flat ground. So I think you probably do just need to push the pedal down a bit more and you'll have the power you are looking for.
 

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2014 Sienna LE
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will try to test 0 - 60 today.
If you are flooring it for a 0-60 MPH test, a few thoughts of mine:
  • Do not floor it until the engine is fully warmed up (coolant gauge has reached it's normal spot on the temp gauge). You want to be easy on engines while they are cold.
    • You won't destroy the engine doing this, and always floor it if needed for safety, even if the engine is cold! Such as to get out of the way of a speeding car or someone running a red light or similar, just don't make hard accelerations on cold engines a habit.
    • Hard use on a cold engine just causes additional wear, so it's best practice to be easy on the engine while cold for maximum engine life.
  • If floored from a stop, my 2014 will spin one or both front tires. I recommend you smoothly but firmly press the pedal to the floor over a period of a couple seconds to avoid this
    • If you get tire spin, back off the pedal until they stop spinning
    • Once you're going 5-10 MPH you should be able to smoothly floor it again without tire spin
    • If you have AWD this likely won't be a concern, may get a little slip until the rear wheels kick in though
  • The engine will get loud as it revs
    • Sounds like you may not be familiar with the engine at the upper half of it's RPM range, so just be ready for this so you aren't concerned
    • The transmission will shift to keep the engine RPM from exceeding redline
      • Even if the transmission fails to shift, the engine has a secondary backup where it will cut the ignition to avoid overspeeding the engine
      • Just mentioning this so you know there are safeguards in place so the engine will not be damaged while flooring it
 

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If you get 23-24mpg scooting along at 80mph with some local, you’re engine is sound. 23-24 is low if you’re lightfooting it at 60mph.

Car magazines get 8sec 0-60 times under ideal conditions with precision timing equipment. If you can get the speedo to indicate 60mph with a soft start as described above with a +/- 1sec reaction time in pressing start and stop in your timing device (phone?), you’re doing well. If you can find level pavement where it’s safe to try and not attract unwanted attention, you’re luckier than I am.

Sixto
‘04 LE FWD 203K miles
 

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When pulling a grade, manually shifting down to 4 from D is usually a good idea. Just remember to shift up to D when you crest the hill.
 

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Although I drive gently most of the time, there’s not a vehicle I haven’t owned that I haven’t floored the throttle on, wether from occasion impatience, just for fun, or most often to get up to traffic speed on an on-ramp (if not behind someone who is not making an effort to get up to speed before merging :mad:).

Happens most often on my motorcycle, for fun, cause 100 HP on a 500 lb vehicle with my 180 ass is just so much FUN to accelerate on. HP/weight ratio of 0.15. The Sienna has a HP/weigh ratio of 0.058, or about 1/3rd the acceleration. With the redline of 11,000 RPM on my motorcycle, I can accelerate from a dead stop to 60 MPH in a couple blinks, in first gear, then let off the throttle and shift from 1st to 5th before continuing to cruise at 60 MPH. So fun! 😁

2nd gear will take me past 90 MPH.You’ll never guess which vehicle I’ve gotten the most speeding tickets on… 👀
I didn't think the motorcycles ever got pulled over....
 

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took the van on a longer drive yesterday (from LA to Santa Barbara) since I took ownership of it. had to climb uphill several times along the way. Seems it lacks power on the climb (2k rpm going at 60 mph), lot of cars just flew by me, be it 4 cyl sedans or 6 cyl suv's. is this your experience? On flat road, it can go at 80 mph easily, shifting is smooth especially after the recent ATF D & F.

Also, it feels slow going from a dead stop, much slower than my Mazda 5 and CRV. i guess that's just how a minivan is?
If you want to go faster on the uphill, more push gas or shift to 4 or 3 from D. The rpm will be between 3k and 4k. You cannot go faster at D(5 speed) on the uphill because of lack of power. I usually shift to 4 when I climb up. The transmision doesn't shift up to 5 while you keep 4.
 

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I also have a 2004 Sienna, 3.3L V6. Some thoughts on your post:
Don't be afraid to downshift manually if you need more power going up a hill. The shifter on a 2004 makes this easy. I used this often while navigating the hills in north Georgia and western North Carolina, for both climbing and downhill braking.
If you know you're going to be in the hills, fill your tank with premium. I know I'll get flak from some folks about that statement, but I know from experience it really helps.
 

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The run between L.A. and Santa Barbara has some steep grades and others that are long inclines that do not look like much of a grade, that may have contributed to the Sienna feeling like it had less power than it really has. Way back when I drove a school bus we would go from Simi Valley to the beaches in Ventura and I was not allowed to drive back to Simi on the freeway due to the Camarillo grade. If you take the Sienna on the 5 north through the Grapevine it will be the same. I have done in many times in my '04 Sienna and as others have said in the thread had to give it a bit more throttle to hold the RPM's up to maintain power or downshift to keep out of overdrive so it did not start to lug. As someone else mentioned the downshift from overdrive to 4th in the Sienna is very easy and the way the shifter is from 4th to 5th (overdrive) is a quick, easy, side to side shift so can be easily done on the fly without looking after the first couple of tries.
 

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Discussion Starter · #33 ·
Went to Joshua Tree national park (Calif desert in the middle of nowhere) for the holiday, open roads with no traffic in the morning, did the 0-60 test. here're the 4 results:
15 sec
12
11
10

I think I started to get the hang of it by the 4th time and should be able to shave off another sec if i push it harder but didn't want to.

question: when downshifting manually from D to 4, do i need to be below certain speed limit? can i be going 80 or 70 and then just downshift. i did play with the manual shift before just out of curiosity but I was going slow.
 

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The transmission should be smart enough to not downshift despite moving the shift lever if vehicle speed is too high for engine revs. I don’t mean that philosophically, there are governors that prevent downshifting.

Sixto
‘04 LE FWD 203K miles
 

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I was in D when doing the 4 tests, no manual shifting involved.
Oh. I guess I read this as you not just flooring it and letting the trans do its thing:

I think I started to get the hang of it by the 4th time and should be able to shave off another sec if i push it harder but didn't want to.
Just floor it. It won't hurt anything. The trans knows when to shift. My impression is from your original post is that you're letting up on the throttle on steep grades to keep the trans from unlocking the TC and/or shifting into a lower gear. Don't. Just let the trans do what it's programmed to do. Really, I use CC all the time. In the rolling hills of Iowa the trans will very frequently unlock the TC and/or shift into 4th. On the 7% grades of Colorado's I-70 the trans will drop all the way to 3rd. That's what it's supposed to do. I won't hurt either the engine or trans.
 
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