Is it just me or .....Electonic Control Throttle-surging
12-07-15, 05:03 PM
#16
Moderator
.... 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 ?
The surging is caused when the feedback control loop is out of the range resulted by some serious failure. The "out of range" is often caused by the too much clogging at the intake line including the air assist line or the poor/slow function of the throttle body as far as I have fixed them all so far. Sometimes the ECU was the cause.
12-07-15, 05:30 PM
#17
Lexus Fanatic
This "surging" was present enough in a brand new 98 LS for us to bring it in. So at least in part it's a characteristic of the car.
10-12-16, 07:19 AM
#18
Lexus Test Driver
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.
fun fact of the day! did you know the current GS since 2013 is full brake by wire? that's right, there is no physical connection between your foot and the actual brakes. when I was in a training class the instructor was telling us all about it and it really freaked me out and asked a ton of questions about it. yes up till 2016 there was still a real parking brake but now that's electronic too. the braking system although electronic, is quite the complex and fascinating system. there is the main brake wire plus 4 backups incase the first fails. and if the battery dies there is energy stored in electrolytic capacitors that hold a charge burst enough to still stop the car...
the real question is, 20+ years down the road, when all those backup wires deteriorate, and those caps go bad like they do, and I mean absolutely guaranteed to fail after a few decades...
whats gunna happen when one day, the brake pedal doesn't respond.
we have been able to enjoy our old 20th century lexus cars, but I truly feel for the kids being born now that are going to be doing, or trying to do the same stuff we are doing now in 2036.
10-12-16, 07:21 AM
#19
Interestingly enough after new motor mounts (both were essentially split in half) the surging is much less of an issue for me. Still kind of there but no where near as jarring as before.
10-12-16, 08:38 AM
#20
By that time cars will all be electric and the only ICE cars left on the road will be owned by eccentric billionaires and hobbyists who are willing to travel an hour to buy gasoline.
10-12-16, 09:14 AM
#21
Lexus Test Driver
truth be told we wont be running out of oil any time soon. plus we have HUGE untapped oil reserves here in the states as well that are not being used because they are on protected land. im sure when it gets down to it, it will be tapped.
when THOSE ones get tapped that's when you know we are in trouble.
10-12-16, 09:33 AM
#22
The switchover to electric isn't coming because we're running out of oil. The world didn't stop using whale oil for its streetlights because it ran out of whales. Electric cars are coming to the masses in a big way, and once the adoption rate hits a tipping point the economics of the gasoline infrastructure become unprofitable. And once something is unprofitable the market drops it like a hot potato.
Last edited by mappo; 10-12-16 at 09:58 AM.
10-12-16, 07:22 PM
#23
Lexus Champion
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
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
https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/831939-accelerator-rod-and-pivot-slop.html
Also, check condition of 78024 which is accelerator cable clamp bracket assembly which incorporates rubber isolation grommet, and doubles as top engine cover mounting bracket... rubber U- channel dries out and seperates from bracket resulting in cable slop...
Applying these two remedies will make a difference and improve pedal control.
Another option to reduce vibration in gas pedal;
https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/807728-lead-foot.html
10-14-16, 11:51 AM
#24
Lead Lap
Have a look at my posting on accelerator pedal pivot;
https://www.clublexus.com/forums/ls-...ivot-slop.html
Also, check condition of 78024 which is accelerator cable clamp bracket assembly which incorporates rubber isolation grommet, and doubles as top engine cover mounting bracket... rubber U- channel dries out and seperates from bracket resulting in cable slop...
Applying these two remedies will make a difference and improve pedal control.
Another option to reduce vibration in gas pedal;
https://www.clublexus.com/forums/ls-...lead-foot.html
https://www.clublexus.com/forums/ls-...ivot-slop.html
Also, check condition of 78024 which is accelerator cable clamp bracket assembly which incorporates rubber isolation grommet, and doubles as top engine cover mounting bracket... rubber U- channel dries out and seperates from bracket resulting in cable slop...
Applying these two remedies will make a difference and improve pedal control.
Another option to reduce vibration in gas pedal;
https://www.clublexus.com/forums/ls-...lead-foot.html
01-18-17, 08:09 PM
#26
Lexus Champion
.... 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 ?
https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/831939-accelerator-rod-and-pivot-slop.html
01-23-17, 03:14 PM
#28
Lexus Champion
https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/828619-negative-grounding-issues.html
The negative ground cables, mounting hardware degrade over time...the original design left room for improvement...don't use cheap stuff in rewire...
The transmission valve body solenoids use a single wire connector which means their negative ground path is through the solenoid body, transmission oil film, lower valve body, metal fasteners,upper valve body, transmission housing, engine block, engine block to chasis ground cable, chassis to main negative battery ground cable...(perhaps I left one out?)(reminds me of early GM songle wire Oxygen sensors.....which were grounded through exhaust system!!! Terrible design)
I anticipate some resistance/voltage drop in this LS400 configuration which does not improve over time.
Contemporary Lexus vehicles have a ground strap between the chassis and transmission housing..this represents an improvement... (although somewhat flimsy cabling) but is not optimal...this could help.
I was experiencing a slight harshness and catch up on downshifts..so I replaced oxidized AC compressor stay and hardware (negative battery cable terminus) and discerned slight improvement.(tried disonnecting and reconnecting negative ground several times before without improvement)
I would also suggest that the ECU should have a negative ground cable (copper) vs chassis ground path...at least loosen and retighten hardware there.
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