Trumpanche

Question for the community with hesitation issues: Do y'all baby the car or are you leadfooted like Lextrician? I'm wondering if the strong correlation between hard driving and good engine/transmission behavior are true with your experiences like it is with my experience.

Latest experiences:
So within the last 4k miles since this oil change, the hesitation issue has come and gone numerous times. There is a VERY STRONG correlation (in my case) to getting stuck in stop-and-go traffic and recurrence of the hesitation. Running the car hard onto the freeway and being first in line at the stop lights seems to be a working cure. This makes me think that my issue is still related to the firmware and adaptive settings and not to engine oil or the like. It's interesting in that it's different from JMcraney's experience because my hesitation doesn't just disappear after a few hundred miles. It's more similar to the guys who say the problem occurs after their spouse/child drives the car for some time (and the spouse/child is probably nervous and babies the car).

It would be nice to not have to drive like a hooligan and yet still have a nice running car. I've noticed that some RX forums talk about periodically pulling the ECU fuse (one guy said he did it at every refueling) to reset the 'learning' in the transmission... The last time I pulled the battery terminals though, the engine's good behavior only lasted one day so that doesn't seem like a particularly promising solution either. Now a solid state relay that only supplies power to the ECU when the car is on... that might do the trick :-)

Thanks!

Devh

The only reason why the car seems to run a little better after the ECU reset is because you cleared the short and long term fuel tables and the car runs mostly off the set tables until the calculation can be made from the sensors to rebuild the tables. During this time the engine will run a little rich with a bit of timing advance and the idle a little higher at the expense of efficiency,emissions and long-term durability of the motor.
Having said that those people who decide to reset their ECU frequently because they think it runs better are idiots that don't understand how it all comes together. It is a good way to diagnose drifted sensors but that's about it.
These new electronic transmissions do take into account driving habits and although they take time to form a pattern they can be easily changed back by just driving and forming a new patten as long as you are the primary driver. It should not be so bad to offset any kind of hesitation behavior that is abnormal.

7milesout

Trumpanche - I mostly baby the car and I have yet to have any hesitation. I've only had the vehicle for 1 oil change. After the oil change it drove just fine, same as it did before.

I baby the car because a) I do not enjoy paying for fuel, and therefore I am b) always trying to get (relatively) high mpg with it, and c) prefer to keep maintenance expenses low (which means brakes), and d) IMHO, it's just plain safer to drive slower. I made my Corolla brakes last 185,000 miles before they were touched. I drive the Lexus as if it were a limo, and I'm trying not to disturb my passengers.

I had to turn the 460's brakes at like 18k miles ... but it was due to the previous owner.

To address your question: I have my doubts that driving it like you stole it actually thwarts the hesitation. But that's just my opinion, since I've not experienced the hesitation.

Doublebase

Correct me if I'm wrong, but long and short term fuel trims are simply a record of an engine's behavior. The computer doesn't look at it and change fuel percentage because of it, but rather it is a recording of the computers adjustments because of other factors. At least that's the way I always understood it. I use fuel trim to help me diagnose problems when there might not be a check engine light to point me in the right direction. I always thought the computer made adjustments based off intake air temperature, air flow, O2 sensor output, engine load, engine speed, vehicle speed, coolant temp, manifold absolute pressure, etc. Then the fuel trim is simply a recording of the adjustments made. The computer doesn't look at its fuel trim and say, well we have a record of us taking away fuel, so let's take away fuel. It instead receives data, then makes adjustments...and records them.

Am I wrong? Wouldn't be the first time.

Doublebase

I drive the same way, mainly because I drive 600 miles a week and don't enjoy buying gas.

Devh

From my understanding from books I have read on the subject because I was deeply into turning at one point.
The long-term and short-term fuel trims are a representation of the fuel tables calculation based on sensor data from the MAF, O2 sensor data and coolant temperature. The long-term fuel adjustments add or subtract in a very large increment. The short term fuel trims are smaller increments within the long-term fuel trim parameters but done in a much shorter period of time to compensate for Air intake temperatures and other factors that needs quick adjustment. If you see your long term fuel trims higher or lower than zero then its compensating and it can be due to modifications like less restrictive air filters and such. If it varies a lot then there might be a problem like vacuum leaks, restrictive airflow from a dirty filter as well as a variety of other conditions. Once those trims max out then you will get a check engine light but it can also occur well before that if you get a misfire or detonation. If you get a check engine light the car goes into limp mode and runs rich to protect engine.
From everything I understand the computers the long-term trims are an indication that the fuel tables have shifted which is used to calculate injector duty cycle to give the car the best efficiency, emissions and reliability. Its constantly being tweaked when the car is running closed loop operation.
But I think you're right, The trims are an indication of which way the tables go.

Doublebase

Ok that's what I thought. I've been to many classes and the first thing they preach is fuel trim. I have used it, it does help at least tell you if its a lean condition or rich...points you in areas you need to be thinking bout, etc.

I wasn't sure if the computer actually used that information to dictate future performance.

Devh

I don't think it uses those values per say but it allows you to see if the computer is adding or subtracting fuel globally from the factory fuel tables.
When the ECU is cleared then the tables revert back to the generic factory, after a few cycles the tables are rebuilt off those.
A good way to diagnose drifted sensors is if there is a drastic change when you clear the computer.
Most 02 sensors except for maybe the newer wide band start to drift after 80k miles and should be changed even if they are still working.

Doublebase

I'm not familiar with the technology behind the new sensors, but I know they are expensive. I think to test them you have to go wide open throttle for a certain amount of time and then the voltage values have to fall within a certain range. I like the old sensors - .1 to .9v - low is lean, high is rich. Heater burns out and all you have to worry about is putting the new one in. On the newer ones on some cars you have to reset the code before you install the new one or the vehicle will burn the new heater out because it's still stuck in full heat mode.

Lextrician

Haha drive it like lextrician. Unfortunately my runs like crap periodically some times I have switched gas stations and seems better. Next it's on to the plugs as I just hit 63000 miles not sure if it's fuel or oil.

Doublebase

My runs a little finicky when the fuel is of lower grade - which I was rotating in with the super every other week. Since I switched to straight super from a quality gas station, it's been fine. I have 100k on mine and I too will be changing the plugs soon.

Devh

I was surprised to find out that my 04 Accord has a wide band 02 sensor so my curiosity had me looking to see if the Lexus has one and it doesn't.
The wide band simply put has lot more resolution/precision and it is used to tune AFR. You cannot tune with a narrow band because it's like an on off rich or lean. I have used a wide band when I turned my other car using a stand alone computer building a fuel table. It also had the ability to use a narrow band 02 sensor in closed loop to add or subtract fuel globally but the map table had to be made using a wide band.

That's sad really and it just adds to the complexity. The heater is only there to bring the 02 sensor to temp so it can start working fast before it's heated by the exhaust. I believe this is done primarily for emissions.
What most people don't realize is that 02 sensors start drifting at around 80k miles and should be replaced. This is the best way to recover efficiency and longevity of the motor.

Devh

One thing I want to make clear so there is no misunderstanding. If your fuel trims are higher or lower it doesn't mean the car is running richer or leaner. The car is ruining closer to stoichiometric or what ever it's ideal programmed fuel ratio is always. The fuel trims show you that it added or subtracted fuel to adjust to the conditions to give it the right fuel ratio.

What you can infer from the fuel trims is that something is trying to make it run rich or lean and the computer is compensating.

Doublebase

Yeah it's always trying to stay at 14.7 to 1, the computer is just showing you how it accomplished that...by adding or subtracting fuel because of other factors. So for instance, let's say you have a fuel problem...clogged filter, etc. you are not getting the proper amount of fuel, so it needs to add fuel to get it to the stoichiometric average...the fuel trim would be in the plus category. A clogged air filter would make it sway the other way, and a vacuum leak would sway it in the other direction.

My 1999 Accord has the wide band O2 sensor - it's the ULEV for California standards. It keeps things more accurate. It also has a double walled exhaust manifold to help the cat heat up faster, it's a pretty cool way to do it. Got to hand it to Honda, all they did was two things to that car and it passed California emissions - and that's the only thing different on the Accord between a ULEV, and a non ULEV...the exhaust manifold and the O2 sensor.

Devh

Honda pretty much pioneered a lot of great technology regarding emission including CVCC and then Vtech. Soichiro Honda was a genius and spent all of his time in R&D not in the board room.

I thought you might like this.
http://jalopnik.com/when-honda-gave-...kdo-1576732771