02-06 Transmission hesitation problems

[wwest]

IMMHO most, or a clear majority, of the complaints of engine/transaxle downshift delay/hesitation in various forums all over the internet seem to involve only the FWD or front biased AWD versions of the Toyota and Lexus 5-speed vehicles.

I disagree. There are many complaints about this downshift hesitation on FWD (I think he meant RWD) also, so this negates the theory of under-steering or over-steering causing these problems. In fact, I was driving my brothers '05 LS430 recently and I could replicate the hesitation as I had on my '03 Es300.

"....clear majority....."

I didn't say, haven't said, that the problem doesn't occur on RWD vehicles, just that complaints of this type are rarely posted for RWD.

So I stand behind my theory for the moment.

[jragosta]

A CLUE......

IMMHO most, or a clear majority, of the complaints of engine/transaxle downshift delay/hesitation in various forums all over the internet seem to involve only the FWD or front biased AWD versions of the Toyota and Lexus 5-speed vehicles.

That wouldn't possibly be related to the fact that the majority of cars on the market today (especially Toyotas) are FWD?

[wwest]

A CLUE......

IMMHO most, or a clear majority, of the complaints of engine/transaxle downshift delay/hesitation in various forums all over the internet seem to involve only the FWD or front biased AWD versions of the Toyota and Lexus 5-speed vehicles.

That wouldn't possibly be related to the fact that the majority of cars on the market today (especially Toyotas) are FWD?

True, but....

Toyota, having adopted the fuel saving features recommended back in 99 by Sierra Research, would have applied it across the product line, Toyota, Lexus, FWD, RWD, AWD and 4WD. I haven't been able to find even one complaint for the nature of the problem as described in the TSB in any Toyota Vehicle other than those with FWD or front biased AWD.

And keep in mind that when VSC is active it assumes control of the throttle valve and the transaxle to prevent or delay downshifting. The two complaints common to the hesitation symptom are delayed downshifts and engine acceleration delay.

Let's for the moment assume that the VSC system falsely thinks the vehicle is under-stearing/plowing. Remember that under-stearing/plowing most commonly occurs on FWD vehicles when the front tires' roadbed traction coefficient is too low for the combined forces, lateral (directional control) and braking or acceleration.

Obviously there would be two versions of the VSC firmware, one for FWD and one for RWD.

Since under-stearing is so highly unlikely in a front engine RWD vehicle might it be totally ignored?

But even if not totally ignored how high might the triggering "moment" be set?

But under-stearing on a FWD vehicle is highly likely, much more likely.

If the vehicle is under-stearing/plowing, not following the direction "set" by the front wheels, how do you control/adjust the vehicle dynamically to devote the absolute maximum front tire roadbed traction to lateral control? You neutralize the engine drive/lag torque by assuming control of the throttle and matching engine RPM to roadspeed based on the current gear ratio, and obviously you cannot allow any pending downshifts. In the case of my 2001 RX300 it actually applies the brakes to both rear wheels on the assumption that whatever roadbed traction might be remaining at the rear can be used to slow the vehicle and thereby help regain traction at the front.

Over-stearing......??

Rare event for FWD, VERY rare event!

And remember that with a RWD vehicle in over-stear one very likely still has the entire level of front tire roadbed traction to devote to directional control/recovery.

Looking back on my 50 years of driving I cannot think of even one instance wherein an unintendional or inadvertent skid, over-stearing, wasn't the result of too much engine torque at rear end. I can only think of one instance wherein my lifting of the gas pedal and/or releasing the clutch didn't quickly result in a skid recovery. That one instance was the result of inadvertently and unknowingly have cruise control engaged (below my actual road speed of the time) on an ice and snow covered roadbed.

Under-stearing.........??

Rare event in a RWD vehicle but common to FWD.

I can only think of one time and that was in the rear engined 78 Porsche 911. My 2001 AWD RX300 has threatened to under-stear a few times but that was quickly overcome by VSC activation in each instance.

So, were it YOU designing the VSC firmware for Toyota wouldn't you make the FWD version "hair-thriggered" as pertains to under-steering? And the RWD firmware "hair-triggered" for over-steering"?

And just mighten that "hair-triggering" cause exactly the hesitation symptom drivers of FWD or front biased AWD are reporting?

Might you even have a "pre-emptive" firmware routine to help alleviate top heavy SUV rollovers?

How would you do that?

Prevent the driver from accelerating into/through a tight turn...

No high engine torque production and/or not downshifts to apply additional torque for acceleration.

[amf1932]

Just a question: Is it "stearing" or "steering", or are they both correct?

[jragosta]

A CLUE......

IMMHO most, or a clear majority, of the complaints of engine/transaxle downshift delay/hesitation in various forums all over the internet seem to involve only the FWD or front biased AWD versions of the Toyota and Lexus 5-speed vehicles.

That wouldn't possibly be related to the fact that the majority of cars on the market today (especially Toyotas) are FWD?

True, but....

Toyota, having adopted the fuel saving features recommended back in 99 by Sierra Research, would have applied it across the product line, Toyota, Lexus, FWD, RWD, AWD and 4WD. I haven't been able to find even one complaint for the nature of the problem as described in the TSB in any Toyota Vehicle other than those with FWD or front biased AWD.

You're systematically discarding any evidence that doesn't agree with your theory. There are reports in this very thread (even this very page) of RWD vehicles with the same problem.

[SW03ES]

No, this problem has been afflicting Lexus vehicles since they first adapted throttle by wire into the LS400 in 1998. The throttle lag presents itself EXACTLY the same in my 03 ES (FWD) as it did in my father's 98 LS and does in his 04 LS (both RWD).

The reason you hear so much more about it on the FWD Vehicles (The ES and RX) is that they sell so much more of them than they do the RWD vehicles, the ES for instance outsells the LS, GS, SC, and IS all combined and the RX definately outsells the GX and LX by a comfortable margin.

I've also driven modern ES' without VSC and they still have the throttle lag.

I know for a fact Lexus gets complaints about this lag in RWD vehicles because they got two complaints from my father.

So back to the theorizing board ;)

[wwest]

Acknowledgements:

Toyota has now publically announced, admitted, that there is now an inherent delay in downshifting their electronically controlled transmissions and transaxles to "protect the drive train". You would not typically engage the clutch with a stick shift before moving the shifter into the "gate", selected gear position. Toyota's automatic gearbox is now preventing the engine from developing torque until the transmission's internal clutches for the selected gear ratio are fully and firmly seated.

This post does not concern, does not propose to address, the "standard" transmission shifting delay as disclosed by Toyota.

A relatively small number of Toyota and Lexus owners, encompassing model years 2002 through 2006, are complaining about extensive downshift delays. These complaints seem to primarily involve FWD vehicles or AWD vehicles with definite front torque biasing and 5-speed transaxles.

This post will focus on just what those few owners might be doing, or not doing, during the operation of the vehicle that might lead to an extended downshift delay period of 1 to 2 seconds.

Technology, ain't it wonderful?

BA, Brake Assist: Just what is this?

Apparently via studies by the automotive industry at large it was learned that some of us are not using our brakes correctly, at least not in all instances. As I understand the implementation, design, in an emergency or panic braking circumstance some drivers apply the brakes quickly, but for some unknown, unknowable, reason then just as quickly slack off the pedal. This might be due to reacting to, being unfamilier with, the resulting pulsations from ABS actiavtion, or it might be a "learned" reaction. Before the advent of ABS many drivers "learned" that severe, hard, brake application would often result in loss of vehicle control.

So the industry decided, on its own, that many of us would be better served if "they" did the "driving", at least in this instance.

Basically BA "watches" the rate at which we apply pressure to the brake pedal. If the brake pedal "stroke" is rapid/quick but then brake pressure slacks off quickly then the BA function is activated and HOLDS the brakes into a heavy application for some predetermined period even with the driver having slightly backed off of the brake pedal pressure.

I may be somewhat wrong about BA in the above dessertation by the important point, aspect, is that BA is being triggered by the "rate of brake pedal travel/activation".

Porsche 997 EBD, Extended Brake Assist:

Same as above but with one added feature.

The processor "watches" the rate at which the accelerator pedal is released. If you lift the accelertor pedal rapidly then the system presumes (second guesses??), that your foot is now headed for the brake pedal and "pre-charges" the brake fluid pressure to move the brake pads from their otherwise retracted position and into "slight" contact with the rotors.

So, we now know that the Toyota/Lexus BA, Brake Assist, system is watching the brake pedal rate of travel to determine if brake assist should be activated. And we also know that Porsche is watching the rate at which foot pressure on the accelerator pedal is removed.

So, given the above as factual, is it really so outlandish to think that the Toyota/Lexus drivers who are experiencing these extended downshift delays aren't somehow, in some fashion, causing these results?

I can tell you truthfully and frankly that my 2001 AWD RX300, when I'm trying to stop on a very slippery roadbed surface just plain does not want to come to a full and complete stop. The anti-lock braking system goes absolutely bonkers! The slower the vehicle speed declines in this circumstance the "busier" the anti-lock systems becomes.

But frankly, that's exactly the way it should operate, allowing me to maintain directional control right down to the lowest IPS (inch per second) travel rate. But what would happen if I suddenly slipped the transaxle into 1st gear? The idle engine speed would likely provide enough engine compression braking to overcome the ABS activity.

And that latter is exactly one of the aspects VSC protects you from.

If VSC detects understearing on a FWD vehicle it will quickly act to alleviate engine driving torque and prevent engine compression braking.

Why would rapid release of the accelerator pedal, or rapid release of the accelerator pedal and then quick application of the brake pedal "falsely" trigger a VSC activation? Or for that matter since the ECU in which VSC functionality is embedded is the "Skid Control ECU" and therefore handles all of the brake control functions, ABS/BA/Trac/VSC/EBD, might not a false activation of any of these functions be the cause?

Porsche is asuming that rapid release of the accelerator is a likely indication of quick subsequent brake use.

What if we follow that tract and see where it goes?

We already know that at extemely low speeds on a slippery roadbed engine compression braking can overcome the ability of ABS to keep the front wheels rolling. So suppose Toyota is preventing shift-downs and/or maybe even commanding upshifts in the same circumstances and for the same reasons Porsche is precharging the brake pistons?

Just a couple of side issues.

Between 2001 and 2004 Toyota moved the two VSC sensors, stearing wheel position sensor and yaw sensor, from a direct connection to the skid control ECU to connection via CAN, Controller Area Network. In 2001 all network communications was via the proprietary BEAN, Body Electronic Area Network.

That might mean that Toyota (or Denso) is no longer in control of the VSC functionality. Bosch, maybe?

When I traded in my 2000 AWD RX300 for the 2001 AWD RX300 I did so primarily to get VSC and HID. I was told at the time that a new feature of trac was to provide a virtual form of front and rear LSD, Limited Slip Differential. I remember wondering at the time that if that was so, brake apportioning being used as a front and rear LSD, then why hadn't they just gone ahead and eliminated the VC, viscous clutch, and used brake apportioning for virtual LSD implementation for the center differential?

They did!

Over the intervening years and the 50,000 miles driven I have come to the firm belief that the brakes are being used to apportion torque front to rear. Very early on I discovered that the VC was almost always "flaccid", almost never stiffened up enough to couple any significant level of engine torque to the rear. On a 4 wheel dyno it took 20 to 30 seconds before the VC stiffened enough to provide ~25% of the engine torque to the rear driveline.

All that is my way of saying, proposing, that there are, may be, implementation aspects of the RX330 engine/transaxle ECU and skid control ECU that are not advertised/published.

Just this morning I asked the service manager at Bellevue Lexus if the there was a method for disabling VSC. His immediate response was "publically available??". And then went on to explain that the one published (disclosed) in AutoWeek worked.

And even after I learned of the existance of several of the unpublished C-best options available for my 2001 RX300 the dealer denied their existance until I came back with a printed copy.

So, what if a portion of the Trac firmware is "watching" the rate at which you release the accelerator pedal and, like Porsche, is somehow preparing the system for a subsequent brake application?

How many of you, given a stick shift on a FWD vehicle, would use engine braking to slow the vehicle if you weren't certain of a high level of roadbed traction? And what about downshifting a FWD vehicle for slowing?

What, no volunteers??

No insanity out there, none?

What if that is exactly what is happening with the owners that are experiencing the extended downshift delay? The Trac system is not allowing downshifts if it expects a quick, following, brake application.

[SW03ES]

What if that is exactly what is happening with the owners that are experiencing the extended downshift delay? The Trac system is not allowing downshifts if it expects a quick, following, brake application.

I'm not reading that whole post, but why then does the ES without trac or VSC have the same delay?

[wwest]

What if that is exactly what is happening with the owners that are experiencing the extended downshift delay? The Trac system is not allowing downshifts if it expects a quick, following, brake application.

I'm not reading that whole post, but why then does the ES without trac or VSC have the same delay?

I don't think anyone has sold an ES series since 2002 without VSC....

[jragosta]

What if that is exactly what is happening with the owners that are experiencing the extended downshift delay? The Trac system is not allowing downshifts if it expects a quick, following, brake application.

I'm not reading that whole post, but why then does the ES without trac or VSC have the same delay?

I don't think anyone has sold an ES series since 2002 without VSC....

VSC was optional on my 2004 ES. I don't think mine has it.

Once again, you should be looking at what other people are telling you rather than discarding all the facts that don't fit your world view.

[SW03ES]

I don't think anyone has sold an ES series since 2002 without VSC....

VSC has always been an option, and I have seen many that don't have it.

Once again, you should be looking at what other people are telling you rather than discarding all the facts that don't fit your world view.

He doesn't do that very well lol

[wwest]

The service manager at Lexus of Bellevue told me that the really simply way to disable VSC temporarily was to create an engine fault.

So I disconnected the MAF/IAT sensor connector on my 2001 AWD RX300 while the engine was running. The engine died almost immediately and wouldn't restart. When I reconnected the MAF/IAT it started right back up but with an engine & VSC failure indication.

After about 4 drive cycles the indications went out.

So for any of you that are experiencing the extended delay/hesitation symptom if you want to try and see if VSC is somehow related.....

[SW03ES]

You're still not listening, jragosta has an ES with no VSC, and I've driven several of them. We already know that VSC is not related to the throttle lag.

[wwest]

Okay, so what's the harm in trying..??

My 2001 RX300 owners manual indicates that Trac was standard on 2WD and VSC on 4WD vehicles. In any case it looks as if the procedure will also disable ABS/Trac/BA/EBD so who's to say it isn't one of these other braking related control functions.

[monarch]

I didn't say, haven't said, that the problem doesn't occur on RWD vehicles, just that complaints of this type are rarely posted for RWD.

What I've noticed after renting alot of '04-'06 Toyotas and other Asian cars recently is that the duration of the hesitation on the Toyota / Lexus 1MZ-FE / 3MZ/FE V6 is greater and long enough to be annoying. The duration of the hesitation in the other Toyota engines and other Asian cars is less noticable and not seriously annoying.

[jragosta]

Okay, so what's the harm in trying..??

Other than wasting energy and throwing up clouds of confusion in chasing a red herring?

If one is really interested in determining the cause of the problem (and eventually a fix), one has to look at it scientifically.

VSC has been eliminated as a potential source of the problem. Move on to something else.

I didn't say, haven't said, that the problem doesn't occur on RWD vehicles, just that complaints of this type are rarely posted for RWD.

What I've noticed after renting alot of '04-'06 Toyotas and other Asian cars recently is that the duration of the hesitation on the Toyota / Lexus 1MZ-FE / 3MZ/FE V6 is greater and long enough to be annoying. The duration of the hesitation in the other Toyota engines and other Asian cars is less noticable and not seriously annoying.

Yep.

It just looks like Lexus was a little too aggressive in pursuing ULEV status. For whatever reason, getting ULEV on the ES required really pushing the limits - and driveability suffers.

Personally, I'd rather give up an MPG or two and have the car more driveable.

[wwest]

"....move on to something else...."

Okay, what about the Trac firmware, or even the ABS firmware having a flaw?

In almost all instances described in the TSB it is highly likely that the driver just removed their right foot from the brake pedal to the gas pedal.

[jragosta]

"....move on to something else...."

Okay, what about the Trac firmware, or even the ABS firmware having a flaw?

In almost all instances described in the TSB it is highly likely that the driver just removed their right foot from the brake pedal to the gas pedal.

Let's see. I don't have any idea what you mean by 'Trac', but as for ABS firmware, please explain how ABS firmware would cause the following:

When pulling onto a freeway, your foot is on the gas as you move down the ramp. You see an opening in the traffic and step harder on the gas. The car sits there for 2 seconds thinking about it and then takes off.

You really have some strange ideas.

[wwest]

Trouble-shooting involves opening one's mind to ALL possibilities.

Many modern day vehicles have some version of Trac (traction control) an off-shoot of ABS. Basically if the car develops wheelspin/slip as a result of too much driving torque on whichever wheels the engine is coupled the Trac system will apply brakes, moderately, to the slipping wheels.

On a RWD vehicle Trac will immediately apply moderate braking to the driven wheels but give the driver a few hundred milliseconds to realize what is happening and take corrective action by feathering the throttle.

On a FWD vehicle wheelspin/slip at the driven wheels, the FRONT wheels, is so much more hazardous that the driver will get no time to react, the engine will be dethrottled simultaneously with moderate braking.

Remember that if the driven wheels on a RWD vehicle begin to spin due to loss of traction you will still have the entire front tires' contact patch to regain or maintain directional control with.

On a FWD vehicle your driven wheels are also used for directional control so preventing even a slight period, a few hundred milliseconds, of loss of traction there is much more important.

The dethrottling of the engine, regardless of drive type, is to prevent over-heating and subsequent warpage of the brake rotors.

[jragosta]

Trouble-shooting involves opening one's mind to ALL possibilities.

Not the ones that have been shown to be wrong.

VSC can't be the cause of problems on cars that don't have VSC.

Traction control can't be the cause of problems on cars that don't have traction control.

Please do yourself a favor and take a course in logical thinking.

[wwest]

Ohay, how do you know that there are not two "forms" of engine/transaxle delay/hesitation? One form which Toyota has deemed "normal", to protect the drive train, and a second, extended one, causing delays of one of two seconds are more.

I can fully and easily accept Toyota' explanation that there is an intentional delay in allowing the engine to develop a substantial level of torque as the downshift is completing. I often drive a stickshift and I do not wish to be replacing the clutch prematurely. So I am careful to not apply gas inordinately quickly as I engage the clutch after a downshift.

So I can fully accept Toyota explanation that the delay is to protect the drive train. But just how long a delay are they talking about? Certainly one that would be noticeable if one were in an especial hurry to accelerate.

But clearly, that wouldn't be 1 to 2 seconds as is being complained about, a few hundred milliseconds, maybe.

So, ALL of Toyota's electronically controlled transmissions with DBW are exhibiting some level of downshift delay. Enough of a delay that any driver having experience with previous, non-DBW transmissions, will definitely notice when quickly returning to acceleration circumstances.

So, what if the anomalous "extended" delay only occurs on vehicles with Trac, or even VSC.

Look at the contention between the parties, posters, involved, some say the delay is hazardous. In my opinion a 1 to 2 second unpredictable delay might very well put one into an unsafe condition. But many who claim to be experiencing the delay contend "no way" to the unsafe or hazard issue, and often further dispute the 1 or 2 second amount.

Good, logical evidence that there may be two forms of the delay/hesitation.

[tdgreer]

I posted several months ago my problem with the hestitation. I have an 04 ES and from the beginning of ownership until now it has been extremely annoying. I appear to have one of these vehicles that has a pretty good case of throttle lag. Lexus performed it's latest update (twice) and it helped just a bit. My 04 is a FWD and I do not see any evidence that it has VSC. Not in documentation or anywhere in the vehicle displays. I know I did have VSC with my 2000 Avalon. It could even be disabled.

Anyway, just wanted to mention that hesitation is a definite problem with my FWD 04, and I'm pretty sure it does not have VSC.

[tdgreer]

Look at the contention between the parties, posters, involved, some say the delay is hazardous. In my opinion a 1 to 2 second unpredictable delay might very well put one into an unsafe condition. But many who claim to be experiencing the delay contend "no way" to the unsafe or hazard issue, and often further dispute the 1 or 2 second amount.

Good, logical evidence that there may be two forms of the delay/hesitation.

I'm not into all this mechanical stuff.. I'm just "a girl". ;-)

But my car definitely falls in the 1-2 second, heck I could just say 2 second delay. Yes, there are times I feel this could put me in an unsafe condition. Particularly when in bumper to bumper traffic or times I need to "get on out there" in fast traffic.

[wwest]

Look at the contention between the parties, posters, involved, some say the delay is hazardous. In my opinion a 1 to 2 second unpredictable delay might very well put one into an unsafe condition. But many who claim to be experiencing the delay contend "no way" to the unsafe or hazard issue, and often further dispute the 1 or 2 second amount.

Good, logical evidence that there may be two forms of the delay/hesitation.

I'm not into all this mechanical stuff.. I'm just "a girl". ;-)

But my car definitely falls in the 1-2 second, heck I could just say 2 second delay. Yes, there are times I feel this could put me in an unsafe condition. Particularly when in bumper to bumper traffic or times I need to "get on out there" in fast traffic.

You don't say if your car has VSC and/or Trac.....

And DAMN, I was just in the Palm Harbor area for the entire week following the 24 hours of Daytona!

[tdgreer]

Look at the contention between the parties, posters, involved, some say the delay is hazardous. In my opinion a 1 to 2 second unpredictable delay might very well put one into an unsafe condition. But many who claim to be experiencing the delay contend "no way" to the unsafe or hazard issue, and often further dispute the 1 or 2 second amount.

Good, logical evidence that there may be two forms of the delay/hesitation.

I'm not into all this mechanical stuff.. I'm just "a girl". ;-)

But my car definitely falls in the 1-2 second, heck I could just say 2 second delay. Yes, there are times I feel this could put me in an unsafe condition. Particularly when in bumper to bumper traffic or times I need to "get on out there" in fast traffic.

You don't say if your car has VSC and/or Trac.....

And DAMN, I was just in the Palm Harbor area for the entire week following the 24 hours of Daytona!

;-)

This from the post I made just prior to the post you responded to: (does that make sense?)

>>My 04 is a FWD and I do not see any evidence that it has VSC. Not in documentation or anywhere in the vehicle displays. I know I did have VSC with my 2000 Avalon. It could even be disabled.

Anyway, just wanted to mention that hesitation is a definite problem with my FWD 04, and I'm pretty sure it does not have VSC.<<

What is trac?