Hey guys, I've had my 16 IS200T F-Sport for about 5 months now, im at 42k miles and I've been recently experiencing a hesitation/jerky feeling when cruising at the same speed. I figured maybe my vacuum regulator went bad again, but the dealer tested it and said it was fine. When going over 20mph, if I have the gas pedal at a certain point the car will lurch forward and backwards, the same type of feeling as you would get driving slow in 1st gear in a manual car. It is more noticeable in manual mode and happens at lower RPM. I can both feel the car lurching back and forth as well as see it on the tachometer. It does not build boost while it's happening since its at a lighter throttle, so the boost gauge is at full vacuum and not fluctuating (Symptom of bad vacuum regulator). Is this an issue or is normal? my only thought is that maybe theres a slight spot/deadzone in the pedal from between where is detects throttle input and no throttle? Any advice would be greatly appreciated, this has been driving me crazy.

 

Hard to say without being there. Post a video maybe? How strong is the lurching. And can you easily replicate the problem. I think you might still have some warranty left. maybe take it in

 

I will try and get a video today. It's strong enough that it's noticeable and bothers me. its easiest to replicate in manual mode. I will also notice it in auto on the freeway if im on a slight downhill slope. I have the 4-5 year unlimited mile warranty. I will try taking it in again, I just have to switch my intake back to stock. It also does it with both the stock and AEM intake.

 

That might have something to do with it. Those kinds of intakes used to cause similar problems in the BMW world too. Today's cars are highly tuned for the specific intake designed for the car so you might get air flowing in a slightly different volume and rate that the software gets confused. Now in theory the car should adjust to it but it's something to consider. Put the stock intake back on and drive it and see if it still does it.

 

I noticed when driving a friend's IS 350 RWD that, at speed, in manual mode, the car does have a slight "thud" sensation when going off-throttle back on-throttle again, particularly at higher RPM. Even the 6-speed exhibits this behavior to a lesser extent. If it's super-jerky, like something that would cause your neck to move, maybe it's an issue. Otherwise, I would probably chalk it up to the way the IS locks/unlocks the torque converter. I've noticed something similar in other cars too, with the best example I can think of being the Genesis G80. When cruising off-throttle, it can be a little abrupt to re-engage when getting back on the power. Just something to keep in mind. If it feels broken, then by all means take it in.

 

I’ve experienced what you’re taking about multiple times. Always happened to me in manual mode at slower speeds with light throttle. I just started to think it was my foot position changing slightly and the car reacting to it stronger since it’s manual mode lol

 

that sounds like the vacuum regulator, i had mine replaced awhile back and its been great so far.
look at the psi gauge for the turbo, if it bounces up and down then thats the issue.

 

Sorry guys it was hard to get a good video while I was driving but you can still kind of see the needle bouncing. I have my foot on the gas slightly to keep speed and it does this. The boost is in full vacuum, so I know it is not the vacuum regulator valve. And it does the with both the Stock and the aftermarket intake so that rules the intake out as well. Could it possibly be the calibration of the pedal?

 

I’ve driven my 200t for over 35k miles now and I can tell you this is exactly how my car drives down to the T! At this point it is something I have gotten use to and use manual mode to try to handle some of the turbo lag as well. I’ve previously did some research and couldn’t find any other Lexus owners really complain at the time but oddly enough the 8 speed in the 2018 Camry which i believe is a different 8 speed, people also report the similar complaints as well. At the time I also did the transmission battery reset so the trans could re learn my driving habits and it did improve a little bit. Another route ORange Virus Tuning has a transmission tune which I hear makes the shifts smoother if that’s a route you are will to go.

 

Yeah that is exactly what I experience as well. So I take it that it is normal then? My previous car was an is350 and it did that as well, but it has 200k miles and the trans was a little rough so I figured it was an issue. If you guys are all experiencing it then I will take it that it's normal? maybe if enough of us complain they can send out a recalibration of the throttle mapping to minimize/prevent it?

 

Coming from a BMW 435 feel likes the car is stalling on the middle of the road as I just got the car and I'm kinda getting used to the tranny lag.

 

I think my 2019 has this issue too, it's hard to describe. I just see it as the transmission not being that smooth, Sometimes I think 8 gears is too much and the car ECU gets lost.

 

My transmission is usually the worst when trying to stop while at high speeds. Also I get rough shifts at high RPM shifts but that is usually normal. Ive just become so use to it i dont notice it anymore . Also you guys probably get those rough jerks when moving out of park when the car is cold.

 

ZF's 8 speed is the world's standard, supreme in every category. perfect 10/10. so i dunno if it's the # of gears. could be the programming who knows. but remember this transmission first came out in the Lexus LS from yesteryear so it's associated w/ and capable of smoothness.

My 200t drove great as far as the trans goes. occasionally like once a month it hesitated to shift (just held a gear for an awkward amount of time) but i chalk that up to software hiccups.

though if you drive any car in any one gear (whether auto or manual) there is the likelihood that the car will lurch back and forth on/off throttle. that's just the driveline absorbing and deflecting the load/shock and is normal. in fact with my 330i, i had M3 engine and transmission mounts, manual transmission, and the car would buck very hard in gear if i let off the throttle and got back on it, like in traffic--and that wasn't a bad thing. that was good. it meant responsiveness. a badge of honor.

so if the lurch you describe is simply the driveline loading and unloading as you drive in any one gear, that's a good thing. it means you drive a sporty/responsive car.

hard to say without being there. i'd probably bet though there's nothing wrong with your car. very very very small chance that can happen. manufacturing is pretty good and pretty consistent.

 

Other than the lurching I always get rough shifts as well, mostly in manual when downshifting when im going slow or upshifting at a lower RPM. Happy with the transmission overall though