Toyota Sienna Forum - siennachat.com banner
1 - 10 of 10 Posts

·
Registered
Joined
·
83 Posts
Discussion Starter · #1 ·
I've got a 2009 with the 3.5. I haven't driven any other Sienna van so have no comparison of performance.
When I accelerate hard thru first gear and it shifts up to 2nd there's a flat spot, then it picks up and runs hard thru 3rd and 4th.

Is this a common complaint and is there a cure for this flat spot?

Thanks
 

·
Registered
Joined
·
83 Posts
Discussion Starter · #5 ·
Over inflate them slightly when it sits and put the volume back to normal before you drive it. One week and flat spots sounds pretty extreme, what brand of tires are they?
I should have been more specific.
I'm talking about a flat spot in the power band.
After it shifts into 2nd under hard acceleration it kinda falls on its face, then picks up acceleration before it shifts into 3rd.
 

·
Registered
Joined
·
439 Posts
Have you done a transmission fluid service? There might be sludge or worn components in the valve body delaying the 1-2 shift. There’s supposed to be timed handoff from 1 to 2. Acceleration can suffer if things don’t go just so.

You might ask if the dealer can flash the TCM. I’m not aware of a key dance to reset adaptations on these transmissions.

Sixto
‘04 LE FWD 203K miles
 

·
Registered
Joined
·
83 Posts
Discussion Starter · #7 ·
Have you done a transmission fluid service? There might be sludge or worn components in the valve body delaying the 1-2 shift. There’s supposed to be timed handoff from 1 to 2. Acceleration can suffer if things don’t go just so.

You might ask if the dealer can flash the TCM. I’m not aware of a key dance to reset adaptations on these transmissions.

Sixto
‘04 LE FWD 203K miles
The transmission is in great shape. This feels like an engine thing
 

·
Registered
Joined
·
439 Posts
Is it different if you shift manually? Accelerate hard in L, bump it to 2 at 6000rpm then to 3 if safe to do so and it won’t get you in trouble. Is it only in 2 that you feel the lull?

The engine doesn’t know what gear it’s in. If it’s not in the 1-2 shift, maybe the gear spacing between 1 and 2 is too wide for the power band. No fixing that.

Sixto
‘04 LE FWD 203K miles
 

·
Registered
Joined
·
83 Posts
Discussion Starter · #9 ·
Is it different if you shift manually? Accelerate hard in L, bump it to 2 at 6000rpm then to 3 if safe to do so and it won’t get you in trouble. Is it only in 2 that you feel the lull?

The engine doesn’t know what gear it’s in. If it’s not in the 1-2 shift, maybe the gear spacing between 1 and 2 is too wide for the power band. No fixing that.

Sixto
‘04 LE FWD 203K miles
It shifts good manually.
The gearing could be too wide but I think it's the factory tune and/or air starvation. The intake duct is pretty narrow.
 

·
Registered
Joined
·
439 Posts
You can check a range of parameters using a $15 ODB dongle and a free app - MAF, fuel trims, ignition timing, etc. I don’t know if a generic scanner will read cam timing parameters which could be a factor.

Sixto
‘04 LE FWD 203K miles
 
1 - 10 of 10 Posts
Top