Did you recently take on (or consider) a loan of 84 months or longer on a car purchase?
A reporter would like to speak with you about your experience; please reach out to PR@Edmunds.com by 7/25 for details.
A reporter would like to speak with you about your experience; please reach out to PR@Edmunds.com by 7/25 for details.
Options
Engine Hesitation (All makes/models)
This discussion has been closed.
Comments
Post # 1099 in the Honda Pilot Problems and Solutions forum states...
"...The hesitation upon acceleration when cornering, I have the same experience with mine too. It doesn't happen from a complete stop, only when cornering in motion. I took mine to the dealer about the hesitation and he couldn't find anything wrong. I just deal with it.... "
Some cars belching a few more fumes than they are supposed to isn't going muck up the atmosphere much more than it is now. The better good would be to fix these cars!
I wouldn't hold your breath for even that. My regional rep has driven my car and declared it to be working perfectly, or should I say, "normally" or within the "characteristics" for the car. (How they can do that with a problem that is intermittant I don't know, but hey, let's not get hung up on facts) I have since been informed that he has even instructed the second dealership that I brought the car to to do nothing in the way of trying to reset my transmission. In short, the Lex rep is now interfering with my efforts to repair the car!
What must we do in order to have Lexus take the car back? Is arbitration the next step? Will they take the car back without that step? How long does the arbitration last? I am wondering if it is better to sell or trade the car now and get out and cut my losses.
Any input is appreciated!
A very adroit observation. You have, I believe, captured the very essence of the problem.
Indeed, it is a big problem, especially when contemplating taking on an adversary with such colossal resources.
"With the advent of the move to (TOTAL) electronically controlled automatic transmissions Toyota/Lexus decided to take advantage of the additional capability to add several new "features".
1. Extend the fuel economy by significantly lowering vehicle "drag" from engine compression braking. Anytime the throttle is fully closed the transmission is automatically upshifted to lower engine compression braking.
2. Significantly reduce the danger of loss of control of FWD, or front torque biased AWD, on slippery roadbed surfaces by reducing engine compression braking.
3. Significantly extend the useful life of the transmission by reducing its "workload" from engine compression braking. Many of these vehicles were shipped from the factory with a transmission fluid life expectency of that of the vehicle itself.
Keep in mind that by the year 2000 the analog, fluid based, "computers" previously used to control automatic transmissions were virtually PERFECT in their overall control operation.
Toyota's electronically controlled transmissions represented a totally new, clean sheet, design.
So, the transmission ECU firmware, software, detects that the vehicle is in a "coastdown" mode, throttle fully closed, and accordingly begins an "upshift" gear change sequence (and/or an unlocking of the torque converter) to reduce engine compression braking.
But what happens if the driver suddenly decides that he/she wants to accelerate at just about the same time the transmission begins the upshift sequence?
The only "feedback" the transmission ECU has to "know" that the previously commanded gear shifting has completed (other than elapsed time)is via a comparison of the transmission input shaft rotational speed and the output shaft rotational speed.
Up until the 2004 model year these transmissions would react correctly to this sudden change of input, quick change from coastdown to acceleration, but by now Toyota had discovered an anomally in the design.
In some instances you couldn't just change the commanded gear selection right in the middle, or during, a previously commanded gear change without compromising the operation of the transmission. The transmission momentarily being in two gear ratios simultaneously, for instance.
So, the 2001 AWD RX300 required no transmission fluid replenishing or replacement for the life of the vehicle, according to the owners manual. But then a significant number of these transmissions began to fail prematurely. The dealers have now been told to advise owners of these vehicles that a 15,000 mile transmission flush and replenishment is recommended.
So, as of 2004 the firmware was rewritten and an e-throttle was added. With an e-throttle the engine can be prevented from developing torque until the transmission can complete the upshift it started at coastdown, and then be downshifted into the proper lower gear for acceleration once the e-throttle is given the GO signal.
A 1 to 2 second delay in acceleration wouldn't be all that unusual in this circumstance."
http://www.autoblog.com/entry/1234000920023135/
Your washing machine has two, one for hot water and one for cold, except in that case 120VAC.
You're in So Cal, right? Where abouts? I'm in Orange County. I'd like to see what a "before and after" ride would be like.
I've been putting off trading up my 2002 to a 2005 (or 06) due to this issue. That pales in comparison to the problems of those that didn't know to avoid these vehicles, and are stuck driving them with this problem.
Nice work. And by a poster that's been a member for less than 30 days!
Can you share the name of this rep, or what office he is working out of? Is he only Toyota or does he also cover Lexus? The Lexus field rep here has been of NO help whatsoever; in my opinion he has now become an impediment to getting my RX300 fixed properly.
But keep in mind how often you have sat waiting for an airline departure while they fix a "minor problem in one of the black boxes" and then you notice they're changing out an engine.
We're not always told the true about these matters.
One of the solenoids is PWM, Pulse Width Modulated, with the 12 volt signal in order to "meter" the transaxle hydraulic pressure as a function of throttle opening.
This borders, a little bit, on the suggestion I made earlier that maybe the hydraulic pump volume within the transaxle wasn't up to the flow requirements if multiple shift sequences occurred back to back, especially if the engine remains at idle throughout.
Ford does this in my Ranger for idle bypass airflow. Using a PWM function on a solenoid is not linear by any means so this is one of the areas were a bit of ECU "learning" would be involved.
In the Ford's case the ECU "experiments" with PWM duty-cycles, factory set approximations, until it achieves ~800RPM and a happy oxygen sensor. Thereafter it "knows" the proper PWM dutycycle until or unless you remove power or change something in the fuel/air mixture path.
I have no idea how the engine/transaxle ECU would "learn" the proper settings (PWM duy-cycle) for modulating the hydraulic pressure control solenoid. But as you can see if something changed, especially within the solenoid itsself, the ECU would, might, continue blindly using the previously "learned" operational parameters until the battery power is removed for a period of time.
My best guess.
a solenoid valve is typically a valve that has an actuator which moves when you apply current to the coil of the solenoid and the core of the actuator is pulled into the coil. typically these devices have a spring return to their "low-energy" "off the shelf" state (which may be open, or closed) such that when the voltage is removed, current doesn't flow in the coil, and the core and actuator are allowed to spring return to the low-energy state. i can imagine a solenoid valve having one flow rate in one state, and another flow rate in the opposite state: the solenoid and associate valve need not be a stricktly full open to permit flow or full-closed to completely inhibit flow device.
i would think that if a solenoid valve fails, it either fails to return to it's de-energized state when the voltage/current to the coil is removed because of sticktion, or perhaps spring wear. it could also fail because the coil winding becomes an open ckt which current cannot flow through, and so it doesn't actuate when commanded. it might also fail because the winding becomes shorted somewhere in the winding, and thus the magnetic force the coil can apply to the actuator's core is off-design.
most probably, the valve is sticking and when either actuated or de-actuated: it is failing to move to the expected state quickly.
i suppose you could also say a solenoid valve will fail if the valve portion itself becomes blocked with debris.
as for Pulse Modulation of the valve, my thinking is this would lead to premature wear. essentially, you'd be playing with what's called the "duty-cycle" (time on vs. off of the solenoid) for the valve to modulate flow or pressure somehow. you'd be defining how long it was in one state vs. the other state per a given unit of time.
rapidly changing the state of the solenoid to achieve this would be rather brutal to the device. i'm not saying they don't do this...but i would think using a servo valve (something that can be commanded some partial stroke) would be expected for finer-grain control.
bkinblk described it as a "problem" with the solenoid. You are right, that could mean that it broke (as I think user777 is describing) or that the design wasn't working out and they redesigned it. Because the hesitation seems to be evident soon after purchase, it doesn't seem like something that is broken due to wear and tear, but rather something where the design wasn't working as it should. The idea of it being a solenoid is confusing to me based on the information we have had to date -- previous fixes have been related to reprogramming the ECM. April 2005 update to the Lexus ES300/330 TSB on the hesitation problem is related to the ECM. The Toyota spokeperson announced a new "software" fix in the April Pittsburgh article. Now all of a sudden it is a solenoid?
SHOULD....APPROXIMATELY...!!
Using a solenoid valve in this manner, as an "open loop" linear "servomotor" with no direct feedback for the ECU to determine its exact position for any given or specific current flow requires a "deterministic" ECU learning software sub-routine since no two "simple" (read INEXPENSIVE) solenoids will be manufactured to the same exacting standards required otherwise.
But as is the case in my Ford ranger, since the downstream oxygen sensor can be used as an indirect feedback device, that shortcoming generally doesn't amount to a hill of beans.
In the Ford I4 when the engine is first started after the battery has been disconnected for some period the ECU uses a factory set ROM (non-volatile memory, doesn't go away with loss of power) parameter. That ROM parameter is really only an approximation, a rough guess, of the probable PWM duty cycle needed to attain the correct fuel/air mixture ratio. Then over time, by watching the oxygen sensor output while maintaining the engine idle at 800RPM the ECU can "seek" and thereby readily determine the EXACT PWM duty cycle required at idle. The factory approximation of this PWM duty cycle is now discarded in favor of the EXACT parameter in RAM (goes away with loss of power).
The PWM modulated solenoid within the Toyota/Lexus transaxle is used to control the hydraulic pressure. Low internal pressure for closed throttle and increasingly higher pressure as the throttle opening increases. My guess is that this, increasing pressure as a function of throttle position, is to simulate the way one would lift the clutch pedal, ease the clutch into engagement, at the same time you apply pressure to the gas pedal with stick shift.
My personal bet would be that the new replacement solenoid will have some type of closed loop feedback so the ECU can more directly determine the actual actuator position resulting from a change in PWM duty cycle. Or maybe an actual hydraulic pressure level sensor as indirect feedback in the same manner the ranger uses the oxygen sensor as indirect feedback to control the position of idle air control solenoid.
Or in the alternative they may replace the inexpensive "simple" solenoid with an actual servomotor. Such as the ones that actuate the hot/cold air mixing vane, fresh/recirc air mix, and the outlet air routing of the automatic climate control system. All of those servomotors have integral feedback poteniometers so the ECU can drive the motor to the EXACT position each and every time.
The design approach I have used personally in this respect is to build a set of parameters unique to each and every solenoid to be used as a linear servomotor, serialize each solenoid valve and be sure that the predetermined duty cycle positional parameters are used where ever that particular solenoid is finally installed.
Either of those approaches is fully and totally dependent on the solenoid operational parameters not changing over its useful life, no additional friction for the actuator travel, no "a few shorted turns of the coil", no debris stuck in the valve itsself.
If I were presented with the problem as we see it laid out before us in the various forums, potentially millions of vehicles involved, at god knows what costs to really do a full recall, I would first try a firmware fix along the following lines.
If the ECU wishes to move the valve from fully closed to mid-point I would first overdrive it, ~75% PWM duty cycle, beyond mid-point, possibly not allowing enough time for the actuator to actually travel beyond mid-point, and then reset the PWM duty cycle to 50%. Basically overdrive it to get it moving quickly to overcome any additional friction that may have developed.
And yet another thought comes to mind.
Suppose the mechanical design engineers, very likely knowing full well of "stiction" as an aspect of controlling a hydraulic valve, didn't relate it correctly to the person writing the firmware specification, or maybe didn't think it important enough to relate at all.
When a servomotor is used to control the position of a hydraulic metering valve it is typical to apply a "dithering" signal, modulated on top of the actual DC control voltage. Basically the dithering signal is used to prevent the valve for coming to "rest" when the position signal is constant for a period of time. If the valve is moved back and forth, ever so slightly, in this circumstance that continuous movement keeps the valve "floating" in the hydraulic fluid and then will move more easily and quickly when the DC position signal is next changed.
You can think of it as a way to keep the hydraulic valve fully coated, "floating" in the fluid just as you might do with a gasoline engine and a lubricating oil pump to fully lubricate the engine before you start it up.
So, the early firmware fix may have been a way to add "dithering" to the PWM solenoid valve to keep its actuator "live" for the next commanded movement, or it may have been an effort to use over-driving as a fix, or maybe even both.
How much is a solenoid anyway (or servomotor if that is what is needed)?
Obviously the solenoid was not failing in any catastrophic way. Nor was the failure intermittent, seemingly. It appears that some random number of vehicles were subject to the symptom, and for those the symptom was quite repeatable and/or predictable.
So very likely an analysis was done, likely on a vehicle or vehicles known to exhibit the failure, and as a result of the analysis a quick and "dirty", inexpensive, firmware fix was decided on.
It didn't work.
So yes, a new PWM solenoid with tightened manufacturing QA control, or even one with some type of position feedback would be a VERY plausible solution in MMHO.
Assuming the PWM solenoid is the one to be replaced.
"The throttle pressure that is applied to the primary regulator valve (which modulates line pressure) causes the solenoid valve SLT, under electronic control, to precisely and minutely modulate and generate line pressure according to the accelerator pedal effort, or engine power output detected.
This reduces the function of the line pressure and provides smooth shifting charactoristics."
The SLT solenoid is energized via the PWM signal of 300Hz. A 50% duty cycle is applied at engine idle.
IMMHO the words precisely and minutely are in no way appropriate to the use of a simple electric solenoid for metering hydraulic fluid flow absent some sort of direct feedback linkage to the controlling ECU.
Now remember, things may be different in the 5 speed, but the SLT in my 2001 RX300 is operated completely open loop. No feedback whatsoever to "tell" the ECU that the solenoid valve actuator have moved to the position dictated by the PWM duty cycle.
The TSB number I was given was: TC 004-03 for "ECM Calibration". I understand that it was issued for April, 2005.
I believe that the transmission in the RX330s are similar or the same as that of the ES330; whether the TSB may apply to you depends on when your car was manufactured.
I hope that this is helpful to those of you who are experiencing hesitation problems with these cars.
This won't take long, and I promise not to appear here again.
A while ago I promised to get with my transmission repair shop owner/friend on return and report to you stalwarts about his formula for dealing with the 5 & 6 speed tranny hesitation characteristic you are discussing.
Did that, plus showed him some of this forum on his office PC.
He looked at some of your many "fix" theories, and speculative conclusions about why it exists, how Toyota/Lexus is the "bad actor", etc., etc.
Many of them made him smile. A few actually caused him to shake his head.
Anyway, he did say you got two things (out of four) that his people would look at when a customer reports a similar characteristic.
You are on the right track about the ECU needing a tweak--and he has the latest Lexus SB--the one which was reputed to be fake but isn't. And it does work!!
You are also right about the solenoid valve fix. It is a possibility in his opinion, but a rare situation.
I'm going to withold the other two areas he spoke about--one of which I mentioned before being chastised by Shifty for my transgressions and got voted out of the Club. If history teaches me anything, it's not to say too much to you stalwarts, because it just starts another round of brinksmanship.
Besides, you won't have anything more to banter about if I did.
My friend tells me the characteristic can be (but isn't always) noticed in all makes using the 5 & 6 speed trannys. He says it isn't a common occurrence and will be noticeable only under a unique set of conditions.
He also said you should have done more research into the frequency of occurrence while searching for solutions. According to him, it just doesn't get complained about often, and it's not exclusive to Toyota/Lexus.
BTW, He agrees with Shifty's analysis of Toyota's position on the issue.
In conclusion, as I said earlier you needn't be concerned about me returning to this discussion--I just felt obliged to keep a promise made long ago.
Cheers.
Jeff
The new recalibration TSB has just been out a month, it is only for the Lexus ES330, your tranny guy thinks the hesitation condition is a rare occurrence, yet he can already say that the new fix works. hmmm. Frankly, I am surprised that he can say it works already. Did he mention how many repairs he has he done so far using the new TSB?
Well, if it works, that's great. Cheaper than a solenoid replacement, I would think. But it would be premature to deem it a success so early in the game, IMHO. I was reading the Lexus ES300/330 tranny problems posts and when the first TSB came out in 2003, it was reported to work at first, but some who continued reporting saw the condition slowly return. Even Wade Hoyt the Toyota spokesperson quoted in the Post Gazette article said it wasn't a 100% fix. If someone does get one of these fixes, please continue to report the results so we can tell if this is the real deal!
Did Toyota come in with a neutron bomb and wipe the place out?
bkinblk, Did they mention that they were ordering your solenoid from Japan by any chance? jc