Jump to content

Hesitation Fix


Recommended Posts

  • 2 weeks later...


Have you actually talked to your service dept? and they say there is a new software update for it??

If so can you get the numbers or whatever they tell ya

Link to comment
Share on other sites

Haven't talked yet, but I know in the past there was something they'd do ... maybe it was just re-setting the computer I believe ... of course now there are rumors out for a fix like the ES, but who knows? I will let you know mid next week.

Link to comment
Share on other sites

Husker, I just talked to my service Girl (hot) anyway she says there most definatly a new program on the way within a short time!!

There is a guy now that is getting his 330 bought back or something at that nature for that problem and lexus is hooking him up in some way...

My mind is wirling on that and a new GS

Link to comment
Share on other sites

Husker, I just talked to my service Girl (hot) anyway she says there most definatly a new program on the way within a short time!! 

There is a guy now that is getting his 330 bought back or something at that nature for that problem and lexus is hooking him up in some way...

My mind is wirling on that and a new GS

I took our 2004 RX330 in for a software update and there is definately a difference now in pick up.

Unfortunately, we do not have it anymore as I just purchased a new 2004 Corvette Convertible to keep my wife happy.

I had traded in her 2000 for the Lexus.

Best to you all.


Link to comment
Share on other sites

OK, just called and made an appointment for Monday to have the computer "re-flashed" as the service guy put it. He said he personally hadn't heard of anything else that was coming down the road as far as fixes, but didn't exactly sound in the know. Basically it just resets the computer to re-learn your driving patterns I believe. We'll see ... I figured it couldn't hurt to have it done. I asked him if it had seemed to have worked for most people and he said he hadn't heard anything else from anyone, so it must've.

Link to comment
Share on other sites

Well Husker, I just called my lady and was told no NEW program is out(they get lexus bulletins out every day)----but there is one coming for the ES and RX for the throttle deal.

So If I were you I would not waste your time going to the dealer because once the computer relearns it will be back to the same ol thing---they are not going to put any new program in there, so its not getting fixed.

I would just wait till the program comes out and there IS one on the way

Link to comment
Share on other sites

Some one asked why disabling O/D and/or manually shifting into 4th might help alleviate the hesitation symptom.........

The root cause of the "engine" hesitation seems to be that the Engine/Transaxle ECU's firmware is designed/specified such that it "wants" to upshift the transmission at any possible time.

Moving the transaxle into the highest possible gear would undoubtedly result in longer coastdown distances, less engine compression braking, and therefore improve the vehicle's fuel economy by some EPA measureable amount/level.

In my own personal opinion it may also be to reduce the potential for loss of directional control due to wheelslip caused by engine compression braking on FWD vehicles.

But be that as it may, if you can reduce the ECU's upshift options, disable O/D and manually downshift into forth, then it is much more likely that the shift sequence controller will not be in the process of commanding/controlling an upshift sequence and will be available to "command" the downshift that you need for acceleration when you next depress the gas pedal.

Someone on another forum had "argued" that the tramsmission upshifting when you release the gas pedal is exactly what it should do and always had done.

There is to me a great deal of truth in that statement so it sent me off wondering and then into some research.

I have earlier stated that my test drive a few months ago in a BMW X3 (definite rear torque biased AWD) resulted in my noting that when I released the gas pedal on the X3 at ~50MPH I got lots, LOTS of engine compression braking. On my 2001 AWD RX300 I get virtually none in the same circumstance.

So I went back and test drove the X3 again.

The difference is that if you fully release the gas pedal on the X3 the firmware seemingly "assumes" that your desire, intent, is to slow the vehicle somewhat rapidly. On the other hand in the X3 if you are in a "mid-gear, say for acceleration, and then you simply moderate, lift the gas pedal slightly, then it will upshift just as the RX300 does.

So the major difference seems to be the variation in what the two vehicles do with a (sudden?) fully closed throttle while in a middle gear.

Link to comment
Share on other sites

My "cut".

There is a rumor that the upcoming fix involves replacing the transaxle's SLT solenoid. That's the electrically actuated solenoid to which the engine/transaxle ECU applies a duty-cycle modulated 12 volt drive signal in order to "minutely" and "precisely" control the hydraulic pressure level used to actuate the clutches within the transaxle.

I had supposed quite some time ago that the root problem might have to do with the volume, capacity, of the transaxle's fixed displacement hydraulic pump.

Case in point....

"Hesitation seems to be much worse, more pronounced, with sudden throttle movement from idle to WOT.

The transaxle's hydraulic pump is directly driven by the engine via the torque converter's output mainshaft/case. The pump's volume capacity would obviously be at it's lowest with the engine at idle. Also, with the engine at idle the ECU's command to the SLT solenoid would be to only sustain minimum pressure.

In other words what fluid volume the pump is capable of pumping at idle is being "bled off" without any substantial pressure in reserve, no accumulator.

And now you suddenly go WOT!

In all likihood the ECU reacts immediately and orders the SLT solenoid to the maximum hydraulic pressure position. But now how many turns of the engine will it take pump enough fluid to build the pressure required to begin the newly commanded downshift sequence?

Begin the downshift sequence too early, before pressure builds, and there is not enough pressure to fully and firmly seat the clutches' frictional surfaces and you end up with premature transaxle failures as is happening with the earlier 4 speed transaxles.

And just suppose you have been a little indecisive about whether or not you can accelerate fast enough to safety merge into that upcoming opening in the high speed lane traffic and your indecisiveness is unconsciously reflected by foot action on the gas pedal. A few slight back and forth movements of the gas pedal could result in initiating an upshift and now you have definitely exhausted any "reserve" hydraulic pressure.

On the other hand.

You are not at all indecisive and when you decide to accelerate you depress the gas pedal to WOT but at a moderate rate.

The ECU will almost instantly release the torque converter lockup clutch and change the SLT command for high pressure and now as the engine RPM rises in response to the increasing throttle opening the transaxle's hybraulic pump flow volume will increase accordingly.

S..m...ooooo..th downshift, QUICK TOO!

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...