Lexus Gs 450H 4gen random juddering, jerking or stuttering..

[Zizan]

Hi all,

The car has 55k miles with original service history to Lexus registred first in 2017 .I drives great but any once in the while after driving the car fast on the highway for longer periods before coming to a stop with or without the foot on the brake the cars starts to juddering, jerking or stuttering.The brakes are ok (checked at the dealer), dealer says it may be bad fuel , but the feeling is something betwen engine stalling and rapidly abs engaging.This happened a few times only after highway driving right before the EV mode enters either during braking or coasting.Pressing the acceleration pedal once seems to cure the hiccups.

English is not my first language so please bear with me.

[stripester]

I have exactly the same problem... Don't know why no fault codes... Watching this thread now... 

[diegolis]

Hi guys, same here…

first time was just after replacing the tires so I thought it was the new tires messing with the abs. It happened just once more and yesterday again but just briefly. So far it happened when slowing down on the highway for the toll, gentle down hill and light braking from 120kph. Its quite violent when it happens. As I understand it, If the engine misfires it shouldn’t make the car shake like that as there is no hard gear engaged so I suspect abs, the transmission or a software glitch that doesn’t quite work out how to downshift from the high gear to the low one when on a gentle braking. Just my 2 cents worth of guessing.
Hoping more versed people read this and shed some light on this issue.

[Steven Lockey]

If it was misfires, you'd 100% have error codes. 

[cruisermark]

Hi

The Mark 3 LS400 suffers from a very similar fault which is down to dirty throttle body - could the same issue apply here - or is engine not running at that point?

[diegolis]

Hi, thanks for the replies.

Can’t say 100% whether the ICE was running due to the startle effect of the shaking but I would say it was on as I don’t remember seeing the EV lcoming up. The shaking started at a speed where the car normally transitions to EV (when all conditions are met) but so far it was only when slowing down from highway speeds with the ICE idling and super light braking. When the Battery is full I know the ICE is not being shutdown to protect the Battery. It’s dawning on me that when slowing down from high speeds with light braking the rate of charge is so high that it goes into protection mode (full battery) at the same time it was sending the signal to shut the ICE down.

With the dirty throttle body does this happen all the time or is it also random?

thanks!

[cruisermark]

With the dirty throttle body it only happens when slowing down from speed e.g leaving the motorway and slowing down - engine turns off !! so you could be doing 50/60 mph with no power steering😨

[diegolis]

Being in that position would be a bit unnerving!

I dont believe that’s the case here, I am more inclined towards either the shifting between the two gears and/or the transitioning to EV but could be anything 🙈

[stripester]

I have the same issue, I'm following this thread and will try to log some data if possible... 

[diegolis]

Let’s see if we can come up with something!
What kind of brakes do you have guys, the bigger brembo with floating rotors or the “normal” ones?

I have the brembos 🤓

[jk850]

was this problem solves?

[diegolis]

Still under investigation, given the randomness of the issue we'll have to wait until someone is really paying attention when it happens and have the spare capacity to monitor the event. That might take a while. I've changed the spark plugs last month (80k-ish kms but 10 years old) and so far it's been running smooth...

[-Jay]

I also have this issue when the engine is labouring under very light load or slowing to a stop. Mine is also over 10 years old so might try the plugs are they difficult to fit ? 

[diegolis]

I ended up with scratched hands and back pain but it was rewarding! Make sure you use proper tools (torque wrench) and follow the instructions on that Russian tech. manual that someone posted somewhere else in this forum. The rearmost on the left bank is the most tricky but it requires just patience...I would start with that one because the rest are quite easy so you are not tired for the most difficult one...or try one of the easier first to get the hang of it and then go for that fu**er. 

amazon B07338KF65 and B09Z1VVW36 are the tools I used. Denso FK20HBR8 are the OEM plugs.

[Lwerewolf]

Pretty sure that you can replicate this effect by running the car in "maintenance mode" or with the engine otherwise forced on and idling (not propelling, not charging the Battery, nothing). It still won't happen reliably.

Mine's a mk3 at almost 410 000kms (250k mi), cold compression numbers last time I checked (a few months ago) were pretty much equal. What is always noteworthy is the amount of oil on the famous 5th cylinder*'s intake tract, and how clean of carbon that tract is due to the amount of oil there. What is also noteworthy is that the mk3 450h's 2GR-FSE engine has a unique to itself part number for the PCV valve - and different intake VVT-i phasers, but I'm more interested about the former. The -FXE in the gs450h is pretty much an evolution of that engine - more compression, even more aggressive late intake valve closing, some other relatively minor differences.

Given the randomness of this issue, I'd say that it's very likely that it's just blowback oil pooling and then being forced in during specific circumstances. Doesn't take a whole lot of oil droplets to destabilize the combustion process of a single cylinder during no-load-whatsoever idling. My 5th cylinder spark plug tends to be a bit more worn than the others too.

I haven't installed a catch can to test this theory yet, it happens way too rarely/sporadically and has been doing this since I got it (at 240k km or so). Sometimes even the incline on which the car is leaning seems to have an effect. If this turns out to be the case, I guess a "permanent" proper solution would be a good air/oil separator system - which would probably involve drilling an oil return line somewhere at the side of the oil pan.

*if you haven't been reading Russian boards, the consensus seems to be that the 5th cylinder compression/wear issue is due to debris going past the air filter (on the mk3 3gs there's no rubber seal along the ends of the OEM filter - hence potential dust ingress) and mostly being funneled to the 5th cylinder (along with oil from the PCV) due to the design of the intake plenum - this appears to be a "common" GR-series engines thing.

[Mr Vlad]

I've read this thread with interest. Having owned a 2012 RX450H for a year or so. That had near 100k miles on it when I had to let it go.

I only used Premium fuel and with an octane booster. The engine oil got changed every 6k miles and regularly I drove it like I stole it. That car Never had issues. No jerkiness or shudders when slowing down from high speed.

For those suffering similar follow what I did, did it with my is300h's and is250. All ran sweeeeeeeet. 

[Mr Vlad]

What was so funny Jay? Please tell me.

[Steven Lockey]

Probably cos your statement is illogical. 
Just because your cars didn't have an issue, doesn't mean there isn't a physical issue with their car not related to fuel.
Lots of other things than fuel that could cause this issue.

[Lwerewolf]

...or just the fact that it's essentially a different engine. Different plenum, different injection patterns, different PCV, water pump and whatnot.

There is a TSB for the pre-D4S RX's re: fuel injectors, though.

[diegolis]

Had it again today, downhill, 4 pax coming to a stop after highway cruise. I believe it's the transmission stuck in the long ratio gear (lower end of the long gear) and the engine stalling like when you come to a stop in 3rd gear with a manual car. Not much info online about the aisin L110 tram, wonder if a TSB or software update was ever released. I believe we are getting close to solving the mistery!