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Engine Hesitation (All makes/models)
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I have no idea what you guys are talking about, but I do appreciate your efforts and the efforts of everybody else participating in this discussion.
It's about time for my 5000 mile service. I'm kinda hesitant (no pun intended) to have the TSB performed...Wish more people were reporting positive experiences about it.
Has it been 5000 miles since your last oil change? The light will illuminate at 5k as a reminder. I believe it is reset it with the odometer, I did this a few k back. More info is in your owner's manual on this. Hope it helps.
bstime, "Lexus RX 330: Problems & Solutions" #1274, 26 Sep 2005 11:35 am
either that or they know there is some attribute about the reflash that isn't good or truly effective for the vehicle...i mean why advise against applying it?
very very wierd.
"Buyers Remorse" can be bad enough when things go well, or as the buyer should expect, when the result is unexpected or not directly a cure.....
What would be your personal conclusion...??
Toyota can't enjoy all the negative attention. That, and they have already shown some measure of willingness to put time and money into finding things to try. But I cannot believe this is an insoluble problem. A new model year changeover often provides hosts of small improvements to many models, by all manufacturers.
Now, I'm not forgetting that this whole mess came about during a new model year upgrade. Before Drive-By-Wire came along, with VSC and TRAC standard, this issue was virtually unheard of at Toyota. Actually, it proves the concept that the product frequently changes at this time of year - it's just that sometimes the new technology doesn't work right the first try. Manufacturers try like hell to prevent it, but imperfect technology sometimes does get sold.
Now back to the "if" - since so many people seem not to have this problem, and there doesn't seem to be any way to prove in court, or to an arbitrator, that this is a real safety issue - there won't be a recall. There's already been some TSB's. But when Toyota get's tired of making their vehicles like this, with this much grief, and all this hyperbole and vitriol, they will make them a different way. Their Executives and Engineers can't be happy to drive cars that have this problem - they have friends and relatives that ask about why their Highlanders and Camrys (and their Lexus up-market cousins) jerk like that, while driving thru parking lots. Someday, the products will change. And not just the firmware - there will be new hardware - faster CPU's, better communications interfaces, AND better firmware. They'll work better, and more consistently better. And when they do, we'll have something specific to ask for. All we can ask for today is something that inspires few to run out and get it.
If they have a solution, it'll be an improvement to the 2006's. I hope so, 'cause for the Highlander, it'll be a complete redesign in '07, with a new design transmission - the 2006 will be a lame duck, last-year model. Plus it'll be a larger vehicle - the RAV-4 is getting a lot bigger this year, and Americans wanted bigger cars - at least during the last 18 months or so while the new model has been being designed. Meanwhile, I'm still reading the Forum, and keeping my fingers crossed for all affected. And awaiting the RAV.
Soooo - anyone driven any '06's yet?
that part i agree with you.
from my perspective - the situation is in part that once solid, simple, well vetted designs are now being replaced by feature-laiden, out-sourced parts-based, multi-vendor integrated, higher complexity systems rushed to market that have their own "smarts"...
and that tend to fail in the most bizzare, novel ways...
making it almost impossible to service (unless it properly self-diagnoses and throws a decipherable code to a computer technology-centric mechanic (? sorry technician), at which point because of same complexity and the rest of the previously mentioned, demands almost full-replacement because the individual parts are not serviceable.
did i mention lowered reliability?
did i mention cost?
i'm not speaking toyota here, i'm speaking about all the manufacturers.
when these systems "work", they seem marvelous, but when they fail...
Now, they've used the ECM's to "protect" the drivetrain - because it isn't inherently robust. They have to rig the throttle response to not allow much torque to be developed or transmitted, in any kind of responsive way.
I applaud their making the safety systems standard - that's what demanded that the VSC computer have a way to close the throttle instantly - called Drive by Wire. But grafting the new system onto the existing system works "just OK" at best - when everything works as it should, it's great. But, as you said, lots of bits are being slung around - thru multiple micro's, via last-generation interfaces, all of which were designed for slower-responding systems. Since Drive By Wire is here to stay, they've got to do better.
Anyone here remember the US built cars of 1974-1982? Two oil crises killed big car sales, and then tighter EPA regs - yikes. Lots of those cars were sold with lots worse driveability problems. They were built that way, and most were eventually "retired" that way. I went right from a 1968 Malibu V-8 to a 1983 Toyota Tercel, and missed a lot of that party.
And...
I'm pretty certain I have seen some note, hype, about the upcoming 2006 models saying that the ECU has been reprogrammed to hold lower gears longer so some level of engine compression braking will be available to help cruise control retrain the speed rise on downhill runs.
These things are essential to your vehicle's smooth running. If it's giving bogus information to the ECM, you'll get hesitations & stalling because the engine will be running too rich or too lean. THere are other sensors that, if malfiunctioning, will give problems like these as well. But none of them have thousands of cubic feet of air flowing through them like the MAF does. Beacause of this, it will get dirty over time, even with clean air filters. If cleaning them wasn't so dang easy, I wouldn't bring it up. But it is.
I've cleaned the MAF sensor in all of my last 5 vehicles, and always got an improvement - smoother running, better idle, and even better mileage (once). Worth a try, in my book.
too bad the EGR valve isn't also conveniently located. i believe it may also be a major contributor to vagueness in shifting, bucking, hesitation.
The primary feedback sensor for the proper/correct mixture ratio is the oxygen sensor downstream of the combustion process and before the catalyst. I don't doubt that the system uses this downstream feedback to compensate, adjust, for long term changes in the MAF sensor's output. And don't forget, right there nearby to the MAF sensor is the incoming airflow temperature sensor, maybe just as important as the MAF.
What, were our cars assembled on the same day, same place? Problem with quality control of a particular part? There's something we have in common that other Camry/Lexus owners didn't get stuck with. I've had the drive-by-wire computer re-set by the dealership twice and the problem is still there. :surprise:
The only firm admittance by the factory personell is that the delay is there to protect the drive train. That could mean anything from preventing engine knock/ping while in an inappropreately higher gear, or to protect the transaxle clutches by delaying the onset of engine torque as the downshift occurs.
I think it has become pretty conclusive that the inception of the problem is when the transaxle upshifts too readily when the gas pedal is fully released, even momentarily.
If the engine were allowed to try to develop a significant level of torque while in the higher gear it would certainly lug and knock/ping, and since a downshift (or two!) is an absolute MUST the throttle must be kept closed for that.
Can anyone explain to me why this was due to MAF sensor (get dirty with 10Km ?) or Oxygen sensor failure ?
There have been posts that indicated a replacement of a MAF cured one vehicle. Based on this one piece of information, I wouldn't spend much time or money on any experimentation. But, cleaning a MAF qualifies - quick and low cost. It takes less time to do, than writing down a well-presented post on theory or explanation.
The thing that make the contamination so insidious is that it's the heated element that melts and vaporizes the contaminants, and thus "plates" them onto itself. The rushing air smoothes it over, and...a shiny surface results.
I use a spray solvent, like brake cleaner, to shoot it clean. I find the less eco-friendly it is, the better it works - the eco-stuff leaves a little residue. It's such a little spray that I don't worry about the ozone layer from this anyway.
I did not suggest this would cure this hesitation problems on all toyota's with this problem, I only shared my own experience with what seemed to sound like the same hesitation that I had in the RX300,Apparently it got misunderstood that the MAF sensors that I swapped from the Toyota to the Lexus were not the same part,If you look back at my response I said I they had the same part number, So that tells me that Toyota which designs both car lines,Tends to share some of the same parts as does Honda and Acura.I'm all for saving a penny! I would rather loose money and retain a customer then for them to tell all their friends.If I don't know the answer I'll do my best to find the right one!
jbuchanan
I've been browsing around the internet, and the 04 RX330 shop manuals, trying to determine how changing out the MAF would result in alleviating the engine hesitation problem.
The 04 Lexus shop manuals indicate that there are two temperature sensing thermistors (resistors that change resistance with temperature) within the MAF sensor module. The first of these is in a bridge circuit along with the nichrome wire airflow sensor itself. The second appears to be a standalone IAT (Intake Air Temperature) sensor.
I have been tinkering with the idea of somehow fooling the engine ECU into thinking there is less (or more??) intake airflow than actual to see if an incorrect MAF signal might resolve the problem.
But then I came across something on Ebay called a "Progressive Tuner".
For $35 you can buy this device that modifies the IAT signal in such a way as to fool the engine ECU into running a richer fuel to air mixture ratio than is ideal from the perspective of minimumizing emissions, no unburned hydrocarbons nor oxygen in the exhaust.
If Bkinblk is willing to try the device I am certainly willing to go on Ebay and purchase one and send it to him.
What say you?
Good description on Ebay just search for "progressive tuner"...
Will there by any CAT degredation? Is the "experiment" detectible at a Toyota service dept. (warranty issues)?
And I'm not proposing an "excessively rich" mixture. Given that running with premium fuel has alleviated the symptom for some folks (seemingly), running between optimum, 14.7:1, and "rich", ~12:1, might do the deed.
And I am by no means recommending a long term experiment, like the "disconnect", a week or ten days should show results one way or the other.
seti "pioneer 10" osprey
Link to my company is there.
Once told Herb Richman that our Falcon Co-processor was:
"The Very HEART of an OLDER machine."
I also know there are some out there who question my motivation in even posting. It is only because I see what I believe to be distortions and unsupported assumptions, and there should be the opportunity to express another viewpoint. On that note, I would question the motivations of someone who directly promotes a specific competing vehicle. A Honda dealer perhaps? I am only kidding there, but I have read similar accusations about my motivations and any sort of assumption of that type should work both ways.
Or does it...??
Let's suppose that when jbuchanan substituted a Toyota MAF sensor instead of the appropreate 04 or later Lexus sensor the Toyota sensor he removed from a nearby vehicle was a model prior to 04.
The MAF sensor module in my 2001 AWD RX300 looks exactly like the one pictured in the RX2004 Lexus shop manual. Obviously there are physically interchangeable and the two electrical diagrams indicate plug and pin compatibility also.
But....
They have different Lexus part numbers, the 2001 is 22204-07010, and the 2004 is 22204-0D030. The 2001 Lexus shop manual indicates that at 68F intake airflow the IAT resistance will be 2.21 to 2.69 K ohms. The 2004 manual doesn't give actual resistance values only that measurements of 98.5 ohms (-40C/-40F) or 156K ohms (140C/284F) continuing for over 0.5 seconds or more indicate a sensor failure.
An acceptable resistance range of 2.21 K ohms to 2.69 K ohms. A ~20% tolerance to measure a 68F airflow.
The 2004 RX330 does not detect an IAT failure, out of range, unless it measures minus 40F airflow or 284F airflow for 0.5 seconds or more.
Suppose the MAF/IAT module jbuchanan removed was on the low end of the tolerance and the one he installed was at the high end? Or even worse (better??) suppose the one he installed was for a pre-04 model year.
What say you, jbuchanan??
It's pretty clear that having a higher IAT resistance for a given "actual" intake airflow temperature would result in a richer mixture ratio overall than one with a lower resistance.
But if it is this simple then why has Toyota and/or Lexus not addressed the issue?
I'm hoping that Lexus will allow me to sort through the available stock and find the one with the highest IAT resistance at room temperature but if not I can buy a "lot" of thermisters in this range and sort through them to find one that is 2.69 K ohms at 68F or close thereby.
Having "soaked" here in the shop at 74.5F all morning this particular sensor's IAT sensor measures 2049 ohms. The plan is to continue to use the module's actual IAT sensor but be able to switch in a resistor in series with it to simulate a colder intake airflow than actual, or a resistor in parallel to simulate a warmer intake airflow than actual.
I will install it in my 2001 RX300 for a few days and try it at both signal modifying settings to be sure nothing untoward occurs.
At the moment I am guessing that the "lean" position will be the one to do the trick. Constantly running a lean mixture would make the engine more subject to knock/ping. Hopefully that will result in the ECU being more reluctant to upshift the transaxle into an area where it's likely to lug down and cause engine pinging.
Hopefully.