A1Posture

.... the Electonic Control Throttle on the 98+ LS 400 is a downgrade from the mechanical throttles from earlier models. I find my car surging forward when I press on the gas from a complete stop. Yes, I can ease into the accelerator pedal to alleviate the "thrust", but that takes thought and application. It's just not as smooth city driving as the earlier models. Does anybody else notice this? Does this affect the 430 as well? What was the reason Lexus went to the ECT? Are there any advantages ?

djamps

I notice the same thing however this is my 1st lexus so I don't know if they all do it. It's not so bad from a stop (IMO, this is typical of most high torque V8's of which I've owned many) but it is unusually bad on the LS when accelerating from a roll -- 1-2 seconds of lag then it jerks forward. Sometimes in traffic I'll put it in snow mode for this reason. ECT algorithms could definitely use a little more finesse on the throttle curve and response time but I think it just is what it is for ECT back in the day.

And interestingly this LS system is not a full drive by wire... it's hybrid -- the cable applies something like 20% throttle directly to the plate and the rest is drive by wire. Probably designed that way as a failsafe since it was a new arena for toyota.

I have owned several 100% DBW infiniti's since 2003 (no throttle cable at all) and none of them exhibited this lag/jerk behavior. I suspect more modern DBW systems/actuators are faster to respond to user input and have a more refined profile than the older systems.

I've read that adjusting the throttle cable might help -- mine has a little play -- but I'm not holding my breath.

A1Posture

Yes! accelerating from a roll is the worst ugh

Stroock639

i think it might just be a characteristic of the car. i think much of it is down to the very smooth yet slippy torque converter the LS uses combined with the responsive and torquey engine. once you learn to take it into account i find it's not so much of a problem. it's more noticeable when your going downhill, it's almost like the input shaft has to "catch up" to the output, but on level ground or uphill you don't get as much of that slack in the drivetrain. if you have a particularly low idle this will be even more noticeable, also make sure your throttle cable itself is properly tightened. if there's slack in the cable it'll be even more noticeable.

benefits? "allegedly" smoother operation, no need for an idle air control valve, more efficient VSC... basically there's no need to push the pedal further down to keep accelerating at the same rate regardless of speed. as you go through the gears and speed up it automatically increases the throttle opening to maintain the same rate of acceleration the whole time. obviously there's some limitations to how long that can be maintained but when i plug my obd ii to iphone adaptor in i can see the throttle opening % increase over time. same thing when you hit resume on the cruise control

http://www.mr2.com/files/mr2/techinf...y.pdf#page=127

i'll let that answer any more questions

dicer

Whether in a car or an airplane I don't think having electronics controlling exclusively is a good idea.
And the system should always have mechanical back ups and a huge emergency button the shut off the electricals. Being an exclusive system opens it up to nefarious stuff. Easy to take over remotely like was shown on the 60 minutes deal, and that was just using known pathways that certain apps can use, what about the onstar like systems used for opening doors remotely and reading diagnostic trouble codes all stuff that is not common knowledge.

Stroock639

it does have a mechanical back up, there's a built in fail-safe that allows operation in "limp mode"

damn dicer i bet you have some kind of apocalypse plan ready to be deployed just in case "s ** t hits the fan" lol... if someone were to remotely control my throttle i'd A) be impressed and ask how they did it, and B) just put it into neutral and shut the car. but hey you never know when Anonymous will strike

Kingsoup

The surging can be an indicator the ECU caps are going too, mine does it sometimes when cold.
Also mine does the thing where you're at highway speed, let off the gas and it takes a half second before it decides to let off the gas, apparently its an emissions thing as my friends much newer VW GTi does the same thing.

dicer

That's the thing about new car stuff, and not sure what years it would have started. But on all the new stuff the ECU's control pretty much everything. There is no turning the key off, yeah it makes you feel like your doing that, but really its a computer that takes that key off command and then acts on it. If the program says nope don't shut off you would be holding a key in your hand racing down the road. And now most cars even have electrical steering, ABS has been in control of the brakes for years, so yeah scary stuff.

alien1974

mine does this too but if i put it into 3 at low speeds, it solves the problem

djamps

FYI I adjusted my throttle cable and the rolling-stop (e/g rolling thru a yield then accelerating) surging is greatly reduced.

alien1974

mines adjusted too, try putting it in 3 if you are driving at low speeds

SW17LS

I remember taking the 98 LS to the dealer for this issue when it was brand new. To a certain extent its a characteristic of the car. As they got better at the DBW throttle, the issue was reduced. I always found driving in ECT PWR helped as well. My 03 ES was WAY worse than my LS in that department. Lexus released tons of transmission shift logic adjustments, none helped. In my ES350 it was gone. LS430 it was gone.

I think considering the fact that the car we're talking about is 18 years old, I think using the term "new car stuff" is a little silly. These technologies have been around a long time, where are the stories of people having their cars taken over by hackers (the Chrysler thing is a different thing than the technology we are talking about)? Electric power steering is just another form of power steering, there is only one car with a steer by wire system, the Infiniti Q50, and it has a backup. My LS has electric power steering...its simply an electric assist motor instead of a hydraulic system. What is scary there? Computers control the application of ABS modulation...not braking...All the mechanical ignition you turn is is a switch. Whats the difference between a switch and a button?

Computers control a LOT in our daily lives, planes, trains, etc. Are there hiccups? Yes...but on the whole its a lot safer now than it was when this technology was not around.

Stroock639

i mean mine "does it too" i think it's all to do with the drivetrain designed to be as smooth as possible. it's almost like the transmission has to catch up to the engine or something when you're in that 2 to 8 mph zone and the rpms drop to idle. once there's sufficient fluid going through the torque converter it takes off just fine.

sometimes i'd even consider this a feature because it allows you to practically slingshot forward if you need to get around someone. need being used loosely here... after driving it enough i'm able to tell if there's a scenario where the car is likely to jump forward if i'm not particularly smooth with the throttle application. just touch the pedal ever so lightly until you feel the slack taken up. and yea like said a loose throttle cable will greatly exaggerate the "surginess"

SW17LS

Yeah as you get experienced driving the car you're able to smooth it out.

djamps

kind of acts like a high-stall torque converter at times. I've gotten used to pushing the gas 'enough' then being patient. Adjusting all the slack out of the cable really seemed to have minimized it tho.