abaitedcat

I have a 2015 non turbo IS250 and when I step on the gas pedal hard, the car seems to shift gear with lag? The car has 46,0000 miles on it. When I'm at an unprotected left turn and the car is at a stop and then when I stomp on the gas pedal really hard, it sometimes lag and isn't as responsive compared to if I had it on sports mode. Sometimes I can see the RPM needle go up followed by the acceleration, shouldn't both happen at the same time? This doesn't happen all the time. If I accelerate slowly and gradually go faster/down on the pedal then it's fine. But if I mash the gas even a little bit hard - to merge for example or to pass on the freeway I notice the lag.

itsx

i think it's due to the gearing of the car. I remember reading somewhere the car likes to hold gears if it knows you're in the middle of a turn. it could possibly be that it wants to hold the high gear for fuel economy reasons, but when you instantly accelerate, there isnt enough torque in the gear at the speed you're in, so it'll downshift hence the lag. whereas in the sports mode, it'll stay in the lowest gear it can at whatever speed you're at and shift accordingly.
like when i'm decelerating in sports mode to a stop, i'll actually notice it downshift. you could probably predict it and just downshift with the paddles until you exit out. just paddle down until you're at the desired gear and once you exit the turn you can just keep flapping it to d8, it wont actually force itself into 8th but rather it understand you're no longer limited the gear range.
i'm not too well versed on how the paddle shifters work when you're in the automatic mode, but it's what i've come to conclude for now

jay90011

iTrader: (23)

You are either experiencing the throttle lag found in all Lexus vehicles. This lag occurs when the ECU has learned your driving habits and tweaks the throttle for you. I would reset the ECU by disconnecting the battery for 10 minutes and reconnect to see if the Lag disappeared after the first 100 miles.
Or you are experiencing Carbon build up but i doubt its this because you would have had several symptoms by now that you did not mention.

Try resetting the ECU first

arentz07

Is there more info somewhere on this learned throttle lag you are talking about? I wonder if I have the same issue. There's about 1/3 second between when I press the gas and the car responds. I assumed all ISs were like that.

350phi

iTrader: (1)

just install apexi accel controller and run it on red setting all the time. problem solved.

abaitedcat

Besides this lag, could there be something else wrong with the car? I just bought the car and driven it for less than 1,000 miles. At first I just assumed it was because I was switching shoes and not pressing the gas right. But then I realized that especially on unprotected left turns when the cars are slowly down and I get a ride, and I have to turn left really fast and hard I can kinda feel the car lag as I mash on the gas. I also tried today on the freeway, I was just cruising at a solid 2 RPM, and then I decided to mash it down harder to get up to 4 RPMs and I definitely noticed a lag as the needle went up and then the car started to take off. All of this is driving on D and regular mode. The lag is pretty much gone with the sportsmode but I hate having to turn it on each time I turn on the car.... and with traffic it's kind of pointless.

Asbel29

abaitedcat

I think maybe it's getting worse in my car because I was on sports mode today and it seems like when I accelerate and then take my foot off of the gas it seems like I can feel some kind of lag or knock or slightly shake in the car ...it doesn't happen all the time though. Should I change the transmission fluid? I'm going to assume it has never been changed before at 46,000 miles. Can I take this to a lexus dealership and have them test drive it or will they charge me for it? I didnt buy it from a certified dealership or anything like that. will changing the oil help? I have net to change the oil since I bought the car so I don't know how old the oil is even though it looks fine and the car drove fine for the past three months.

qua1ia

I just bought a IS300 and also notice a great deal of throttle lag. Maybe resetting ECU is best way? Some cars have ways to reset throttle response using pedals..

dizlex

ECU's that "learn" your driving are an old wives tale. I've not once read of any such thing, from a reliable source.

dizlex

Are you sure that the ABS is not kicking-in?

abaitedcat

Im not sure about anything. It seems like the lag is not an issue, but the issue is on sports mode now and sometimes when acceleration harder the car kicks or jolts a bit.
Also when I mash the gas pedal and then take off my foot right away theres also can be a jolt. This problem isnt always consistent. It might just be me?

Also, when shifting the transmission is it supposed to make a swoosh noise and kind of click into place or is it supposed to be quiet?

arentz07

I assume you mean traction control or stability control, right?

jameshan

iTrader: (1)

This is partly due to why I always drive in manual so I can stay in lower gears until I know I'm going to be just cruising with no need for acceleration.

Ajowhan

iTrader: (1)

Yup, I definitely feel the difference in sport mode vs normal. I think that there is nothing wrong with your car. I think they are just programmed that way so when you are driving normal, the car drive slower and when you are driving sporty, the car provides its max responsiveness. That way, you really feel the sportiness in sports mode.