90- Series V6 3,4 A343f What could possible be wrong

[Swedishfish]

Hi Everyone
I just entered the new life of Toyota but i have some struggles. The challenges is intermittent. Some times/quite often the gearbox is keen on changing gear to the lower. Almost like is is stuck in kickdown. slightly load and it is changing gear. Some times during acceleration will not the car change up gear. it only change gear when I lift of the throttle.
What have done so far.
I have flushed the transmission. i tried two different typed of transmission fluid, Running now Dexron 3.
I have change the TPS Throttle positioning sensor but no change.
When I run the car with out TPS the car shift good but it only shift depending on speed. there is no " kickdown" function.
I tried running the car with out rear speed sensor but made no difference. only OBD told me zero speed and the instrument cluster showed me 0 speed,
I looked inside the ECU for any problems or moister but it looked good. I tried replacing the ECU from similar car but it dose not start due to immobilizer. That ECU looked also good inside.
I have adjusted the Pressure line but it dose not matter. The problem is intermittent. Some times this s*** happens.
My suspension is that it is ECU issue. I am thinking of building a Arduino controller just control the gearbox better.
Dose any one now how to remove the immobilizer so i could try the other ecu i have.

Best regards
Victor from Sweden

 

[Swedishfish]

When i compared the two ECU i found a small Yellow part. i don't know what it is. is 1mm times 1mm in size. It is one the ECU that is in the car,

Any clue What it could be?
Nothing on the other ECU have with has the dam Immobilizer.
Victor

 

[AirheadNut]

I would suggest changing out the shift solenoids in the transmission. When they go bad it will no longer shift properly, and they are relatively cheap and easy to replace. I had the torque converter lockup solenoid go out on an A343f, it was very similar to what you describe; it would randomly unlock the torque converter, and it was worse when the transmission was warmed up.
The process is pretty simple, just drain the fluid out of the transmission pan, drop the pan and the three solenoids are right there. While you're in there it is a good idea to clean the filter screen.
Here are some photos of when I replaced mine, this is on an LJ78 but the transmission should be essentially the same inside.

Builds - 1990 LJ78 in Montana

Those aren't rattles .... That's simply the land Cruiser having a conversation with you. :)

forum.ih8mud.com

 

[Swedishfish]

I would suggest changing out the shift solenoids in the transmission. When they go bad it will no longer shift properly, and they are relatively cheap and easy to replace. I had the torque converter lockup solenoid go out on an A343f, it was very similar to what you describe; it would randomly unlock the torque converter, and it was worse when the transmission was warmed up.
The process is pretty simple, just drain the fluid out of the transmission pan, drop the pan and the three solenoids are right there. While you're in there it is a good idea to clean the filter screen.
Here are some photos of when I replaced mine, this is on an LJ78 but the transmission should be essentially the same inside.

Builds - 1990 LJ78 in Montana

Those aren't rattles .... That's simply the land Cruiser having a conversation with you. :)

forum.ih8mud.com

I have already changed all 3 solenoids, S1 S2 and Luckup and new filter. One solenoid was bad of the old and i could not go in to second gear at all.
The only problems now is the shifting points. Even when the gearbox is not behaving it shifts but won't hold gear.
Victor















.

 

[Swedishfish]

Hi Gents
Yesterday i made some progress. I hade some suspicions that the forward speed sensor was bad, I disconnected the forward sensor. The TCU will then use the rear speed sensor instead.
Now the car shift superb. Only problem is OD is flashing and i need to drive over 40Km/h once to get the TCU use the rear speed sensor.
I am going to order a new sensor ( looks like a hall sensor) and mount in the gear box

 

[Bardiya]

PM sent

 

[Swedishfish]

I have change the senor and now she is working as good as new.

 

[bigredmachine]

going back to previous question with the immobilizer i would expect that to be a separate ecu, its usually hidden back behind the dash in a very inaccessable location for security reasons. i dont think that the yellow mark is anything, it looks like its just a paint pen mark that may have been used when the ecu was assembled.

you could bypass the immobilizer by getting a bypass unit from a remote start if you have to figure something out

 

[lugueto]

I think you're overthinking this..

A343F kickdown is cable operated. There are two cables on your throttle body, one is your accelerator pedal the other is your kickdown.

Too much tension on your kickdown cable will make the transmission downshift too quickly. Too little tension will cause her to feel sluggish. I'd recommend you adjust this first.