Lag/throttle transmission - short term fix (please test) (2 Viewers)

[EscapeWagon62]

All,
I'd ask that a few of you test this.
Many of us are experiencing some issues with transmissions. On the 24s it's mostly around lag in throttle response at slow speed (rolling stops etc.) as well as significant lag in downshifting under heavier throttle (unlike the 2023s that have studder, hard downshift etc)
For the past 6 days I've been running an experiment where I deactivate PCS. My hypothesis was that a safety system was killing throttle input vs the transmission being incapable.
The improvement in noticeable at 4 way stops (where you don't come completely to a stop), rotaries etc.
The odd thing is that it also seems to solve the lag in downshift at higher speeds (transmission is much more responsive).
I dropped by to see my favorite Lexus tech to share this which he will pass along to corporate. He also asked me to try out keeping PCS on but lowering the sensitivity which I'll do.

He also asked if some others would do my PCS off trick to see if it's just in my head or if it actually works.

 

[Oakleyguy]

I

All,
I'd ask that a few of you test this.
Many of us are experiencing some issues with transmissions. On the 24s it's mostly around lag in throttle response at slow speed (rolling stops etc.) as well as significant lag in downshifting under heavier throttle (unlike the 2023s that have studder, hard downshift etc)
For the past 6 days I've been running an experiment where I deactivate PCS. My hypothesis was that a safety system was killing throttle input vs the transmission being incapable.
The improvement in noticeable at 4 way stops (where you don't come completely to a stop), rotaries etc.
The odd thing is that it also seems to solve the lag in downshift at higher speeds (transmission is much more responsive).
I dropped by to see my favorite Lexus tech to share this which he will pass along to corporate. He also asked me to try out keeping PCS on but lowering the sensitivity which I'll do.

He also asked if some others would do my PCS off trick to see if it's just in my head or if it actually works.

I experienced this severely in my GX550. Sport helped reduce the issue a little.

Have not experienced in the LX7, so it seems they've improved the throttle/transmission mapping a bit.

 

[Joe T]

These definitely have some drivability issues. Toyota/Lexus is lacking some corporate discipline between departments.

I will try it out today, but its raining. We are experiencing the same thing and its the downshift into first at 3mph.

Downside is I run my avoidance stuff on high, not experiencing a detune on other makes. I can be distracted at times and my current PA just turned 20 and is only on a drivers permit (teaching her).

I am going to change the transmission fluid to Redline D6 or Royal Purple 01320. Haven’t had time yet. Try to get it a little more responsive before I tune it. Honestly have been contemplating going Lemon Law which is why I haven’t touched the tune I have waiting for it.

Also go with a thicker oil as per my 5-30 thead.

 

[eNx]

I'm pretty sure that the PCS has some part of the weird driving dynamics. I already knew it either apply the breaks or regeneration-breaking because the car slows down as if I was breaking when I just let my car off the throttle, then if your apply some throttle while it's breaking, you feel a little jitter. This also happened on my previous RX 500h and when I had a Subaru Outback with Eyesight. So in a sense, I'm use to it? But I feel like Lexus should be more refined than my Outback.

I'll try it later today, with PCS off, and will report back.

 

[Joe T]

Try it in manual mode and the torque converter logic changes. The bucking motion you mention is less noticeable.

The torque converter logic is based around MPG and they want the exhaust sounds when slowing down as well.

Quite frankly I have owned quite a few vehicles including SMG transmissions and this is the most temperamental junk I have experienced.

If I wasn’t a car enthusiast set on fixing it I would have got rid of it already.

Don’t fool yourself on the MPG stuff, this thing is tuned all around that.

 

[Joe T]

So far with it off that bucking motion is pretty much non existent. Throttle response better. Less hesitation at shifts.

Still has the first gear shift lag.

I set the software so it remembers the last setting at start up with PCS and will leave it off for now. Between this and the heavier oil its doing much better.

 

[EscapeWagon62]

Ok - I’ll try a few more 4 way stop signs, rolling stops and merging situations. And from what mthe tech told me theyve had zero issues on 700s.
Thus far my 2024 600 delayed throttle response seems to have disappeared with PCS off and better than previous when PCS is set to minimum range. It also shifts better when passing/merging onto freeways.
I know lexus is focused more on the GX jutter but I’m trying to get kore attention on LX. The GX issues seem to be similar to 2023 MY LX

It doesn’t solve all of the issues but if ai can solve this one I’ll be satified.

If it helps multiple people then I can get my buddy the Lexus tech to start narrowing Lexus’ focus. He said it makes sense on the low speed improvement, the mid and high speed gear change improvement is a head scratcher.

 

[Joe T]

My build date is 4/24.

It still has the delayed 2-1 downshift. I mean all they have to do is bump the 2-1 downshift up to 7-8mph…. It definitely gets confused trying to start accelerating between 2-4mph and/or revvvvs like crazy to get into boost even when accelerating from around 5-8mph. Taking off in second is the same as taking off in first with a 2.20 axle ratio.

As far as the rest, turning off the PCS improved power because same throttle input with it on while cruising mildly accelerating making it down shift doesn’t happen as easily with PCS off. Seems to buck less too when coasting but still does some.

Yall try that. Accelerating slightly around 35-50mph with it on and off and see if I am crazy… or not. Has more power and doesn’t need to downshift.

I have the software set to keep it off when restarting it and will leave it this way.

I also highly recommend changing the oil to mobile1 5-30 or 0-30 european. That really smoothed out the jerky moderate acceleration issue. I will do the transmission and transfer case next to something less environmentally focused.

 

[eNx]

First part of the video, he talked about regen breaking. Good info. I didn't know that if you want to test the hydrolic break, you can put the car in Neutral and regen breaking will be disabled.

 

[EscapeWagon62]

For this particular issue it is solely a gas engine issue.

 

[Joe T]

Post your build dates too.

 

[EscapeWagon62]

Build date 8/24

 

[doktorno]

8/11/23 Build date. My impression is my '23 almost never hits 1st gear from a stop sign, feels like if I am rolling the stop it stays in second. I run PCS in the lowest sensitivity setting, FWIW. I have not complaints with the transmission, but I feel like I have trained my right foot to work around the sensitive throttle.

 

[Joe T]

Man I feel mine has more power while cruising with it off. Try it, same road and speed on and off, same throttle level, and it seems to need to downshift more with it on (less power available).

I originally told Lexus I thought it was something with the traction control system that was causing the throttle jitter.

Anyway, the bonus is I figured out a way to save the settings so I can cruise around off road without having to turn this s*** off everytime I turn the car on and off. Carista tuner

 

[EscapeWagon62]

Thanks @Joe T
Did you post a thread on the Carista tuner? I might want to do that

 

[Joe T]

On lexus forum under how do I disable seat belt chime thread. At the bottom.

 

[EscapeWagon62]

Ok - looks like we are on to ONE of the issues.
1. We know that turning PCS off helps with delayed throttle response at low speed and seems to help make the transmission more reactive to throttle input at normal speeds.
2. We know it has no effect on 2022-2023 transmissions as it relates to delayed shifting from 2nd gear to forst gear. THIS is the primary issue Lexus is spending their time on a corporate as the GX550 is getting serious complaints.
3. To be determined if setting PCS to minimum distance generates the same improvement as it does in bullet point #1
4. One area in bullet point #1 that im still testing is normal speed, high throttle input while driving downhill. Ive noticed it is very slow to downshift in this situation which leads me to think some type pf torque sensor is also involved.

Lexus will eventually sort all of this out. I am just trying to find areas where they can look. As mentioned in one of my other posts, 90% of their time is being spent on GX550 (bullet point #2 anomaly) due to higher volume and higher “1st time Lexus” customer base.

Keep the feedback coming.

 

[eNx]

The problem of turning off pre-collision, you lose cruise control, which IMO, is more important than the jitter. Then again, as I posted in my previous post, that I'm use to it.

 

[Joe T]

I wasn’t aware of that. Only have been in town. It certainly has less studder when pressing the accelerator at moderate speeds. Seems to have more power too, less downshifts needed while at cruising speed with moderate acceleration.

If you want to gripe about the delay, show them how you can manually downshift to 1st between ~4-7mph and still get the bump/kick delay when trying to accelerate.

I hope a fluid change then programming fixes all this.

 

[EscapeWagon62]

Two quick updates on this.
As a refresher, this was solely part of my search to address the lack of throttle response at rolling stops/merging onto busy streets etc. (i.e. unrelated to delayed downshift from 2nd to 1st that 2022 and 2023 model years seem to have)
I have a few hundred miles testing PCS off and a few hundred miles testing it with PCS set to the lowest level of sensitivity.
What I have found is that setting it to minimum sensitivity, while not in my opinion as good as turning it off completely, makes the vehicle perform acceptably. Essentially good enough to drive with confidence in all situations I’ve experienced.
I no longer fear 4 way stop intersections, it seems ro be more lively both in throttle and in downshifting for passing.
I finally feel like I have a vehicle worth keeping for decades.

I did have my Lexus tech call Lexus and file a new technical case and I will work to have one of their field engineers look at it when I come in for my 10k service. No doubt they have other issues to address on 2022s and 2023s but this one function HAS to be an easy fix.

It’ll be a while till I hit 10k (at 6,700 now) but in the mean time I highly recommend setting your PCC to min distance and only use PCS off if your driving conditions include major stop and go, congested freeway use. I live in Western MA where neither of those are common.