Mk4 Ls400 - hesitation treatment

[cornershop]

I've had my 98 LS400 for around 4 months now, and from day one its suffered the low speed hesitation issue when executing low speed turns or any scenario where you slow right down, then speed up again without stopping. The revs build, but speed doesn't and then with a jolt, everything syncs up and you're launched down the road somewhat embarrassingly.

I've taken a 'lazy git' approach and reached for a fuel treatment, hoping to clean the injection system, prior to removing the throttle body for cleaning at a later date.  I'm a sucker for wonder products, and this one seemed to have some decent reviews:

http://www.powerenhancer.co.uk/archoil-ar6200-fuel-modification-complex-high-concentrate.html

Over the past 3 months (circa 1k miles), i've used the highest recommended dose of 1ml treatment to 5 litres of fuel on 3 occasions now, and have noticed a difference straightaway in terms of improved pick-up, throttle response and acceleration.

Best of all, the hesitation is vastly improved - i won't say its gone completely, but in the last 50 miles or so, I can't say i've noticed the aforementioned symptoms.  I've not checked mpg, but most reviewers seem to have experienced some improvements.

The treatment is not cheap but appears to work in terms of general performance benefits (throttle response, pickup etc) and protection against ethanol content.

I'll report back in few months time to see if its still working.

 

 

 

 

[Matt1986]

8 hours ago, cornershop said:

I've had my 98 LS400 for around 4 months now, and from day one its suffered the low speed hesitation issue when executing low speed turns or any scenario where you slow right down, then speed up again without stopping. The revs build, but speed doesn't and then with a jolt, everything syncs up and you're launched down the road somewhat embarrassingly.

I've taken a 'lazy git' approach and reached for a fuel treatment, hoping to clean the injection system, prior to removing the throttle body for cleaning at a later date.  I'm a sucker for wonder products, and this one seemed to have some decent reviews:

http://www.powerenhancer.co.uk/archoil-ar6200-fuel-modification-complex-high-concentrate.html

Over the past 3 months (circa 1k miles), i've used the highest recommended dose of 1ml treatment to 5 litres of fuel on 3 occasions now, and have noticed a difference straightaway in terms of improved pick-up, throttle response and acceleration.

Best of all, the hesitation is vastly improved - i won't say its gone completely, but in the last 50 miles or so, I can't say i've noticed the aforementioned symptoms.  I've not checked mpg, but most reviewers seem to have experienced some improvements.

The treatment is not cheap but appears to work in terms of general performance benefits (throttle response, pickup etc) and protection against ethanol content.

I'll report back in few months time to see if its still working.

 

 

 

 

My 98 mk4 does the same thing. So this is a throttle body/fuel issue? I assumed it was a gearbox trait not engaging the power properly due to being confused in slow speed starts. I'd be really happy to find a solution as it's quite annoying sometimes!

[Tinonline]

Sounds a bit gearboxy doesn't it?

But as you say the box takes signals and might be a bit slow to respond.

I'd check the basics: when air filter and plugs were changed. Do you have too much slack in the throttle cable? 

An ailing airflow meter will cause these issues but in my experience once these go, they really go and pack up. So the car will stall at tickover and unplugging it is the only sane way to get home!

Could be throttle body related. I doubt cleaning will make huge differences as they don't get so clogged up they do this kind of issue but the sensor can fail. I do caution cleaning as there is a protective film on the surface and only correct cleaning agent should be carefully used. 

I doubt there is a gearbox fault...

[cornershop]

 i too thought the worst that it may be transmission related, but then i thought it would be a lot more prevalent, rather than happening intermittently if it were transmission.  The fluid is still cherry red, doesn't smell burnt and I've adjusted the throttle cable to remove some slack - this didn't help with hesitation at corners, but did make changes softer and less noticeable.

[cornershop]

This was the post I referenced when investigating - scroll down to a post from Yamae :

http://us.lexusownersclub.com/forums/topic/49570-transmission-hesitation/#comment-478201

 

[alien1974]

mine does this too, i find if you put it in 3 when driving round town ie 30 mph it solves the problem when it comes to the slow down speed up lurch 

[cornershop]

Just back from a circa 90-100mile round trip, involving a mix of m-way and town driving, involving a fair bit of stop-start traffic as you can imagine between London and Surrey.  

Happy to say I didn't experience the issue once in this time.  

It does appear that I've overdosed on the treatments I've applied, in that I've used 20ml per 70 litres instead of the recommended 20ml per 100ml.  

To be on the safe side I will get an oil / filter change when I get the mot done in June (strong fuel treatment can lead to dilution of the oil, especially so in a thin /30 oil)

[Cotswold Pete]

On 07/05/2017 at 9:17 AM, Tinonline said:

Could be throttle body related. I doubt cleaning will make huge differences as they don't get so clogged up they do this kind of issue but the sensor can fail. I do caution cleaning as there is a protective film on the surface and only correct cleaning agent should be carefully used. 

I doubt there is a gearbox fault...

Had same issue with mine, and last service had throttle body cleared out, and hey presto no problems wierd cold starts, gear changes, near stalling.

I assume additives do the same thing, just takes a bit longer. 

[maxwellwd]

Its odd because I had this exact same issue which got worse, especially once the car got up to temperature. Like some of the posters above I thought it was transmission related as I checked the fluid and was a dingy colour so I got the car booked in to have the trans fluid drained and refilled. It still didn't fix the issue, my mechanic said it was almost a misfire, they recommended to change the plugs and HT leads. Once they did that it cured the car completely and has never happened since. 

I think the previous owner had skimped on a plug change, worth getting done for peace of mind I would say (mine is a MK3 97) 

[Newbie1]

I've noticed this ever so slightly on mine (70k, throttle body clean as a whistle when last checked, sparks new etc.). My assumption was that it was somehow connected to the traction control system. What I have noticed is that if I drive it in snow mode the changes are smooth and pulling away presents no jerkiness (around London snow mode is fine, really, as you never pull away or get anywhere at any speed!). However, cornershops post is interesting, although is it the case that the magic formula is really some sort of octane booster, which might explain the improvements in performance? I have noticed that the LS400 is happier on super than regular.

[Cotswold Pete]

20 minutes ago, Newbie1 said:

I've noticed this ever so slightly on mine (70k, throttle body clean as a whistle when last checked, sparks new etc.). My assumption was that it was somehow connected to the traction control system. What I have noticed is that if I drive it in snow mode the changes are smooth and pulling away presents no jerkiness (around London snow mode is fine, really, as you never pull away or get anywhere at any speed!). However, cornershops post is interesting, although is it the case that the magic formula is really some sort of octane booster, which might explain the improvements in performance? I have noticed that the LS400 is happier on super than regular.

I think I might try Snow Mode, kind of makes sense, and assume it does not add to fuel consumption.

Also tried Super a few  times, but cannot say I noticed any difference in the way Mk4 or previous Mk3 ran.  Maybe more town driving is where Super comes out better

[Newbie1]

I'm probably imagining the difference as between regular and super! I know that it shouldn't make a difference, really.

The link to the US site is very informative. The gear change issue is like on an old MS65 Crown Super Saloon I had which did the same thing, although that was just ancient Toyopet auto box behaviour.

[cornershop]

8 hours ago, Newbie1 said:

, although is it the case that the magic formula is really some sort of octane booster, which might explain the improvements in performance? I have noticed that the LS400 is happier on super than regular.

There are no claims of a higher octane from what i've read in the link.  As well as cleaning abilities, it offers an improved fuel burn, fuel stabilization however i can't see either of the latter improving a sticky throttle body - I could be wrong?

I used some BG MAF cleaner and cleaned the air inlet mix path - made a subtle difference to idle and pickup, but did nothing for the hesitation.

[runsgrateasanut]

Before the 1200 mile hike I've just done I put in a full bottle of injector cleaner (perhaps too much?) at Dover and the usual 95 octane.  Only needed two top ups while in France but had to use SP98 which I personally think that the Car doesn't like as much as the lower octane. 95 is only sold as E10 in France which I have read can destory an old engine so 98 only way to go and admittedly I use Supermarket / Le Clerk which saves 10c a litre so maybe not the best grade. Never had a problem with jerkiness although using Cruise I did think maybe there was a hesitation or could have been the way I disengaged it. Not sure if there are rules to follow on Cruise which I'll check. Most times I just pulled the lever forward to disengage and then pressed the button, but maybe I pressed the button only to disengage on occasions?  Cruise is geat for going up hills but I don't like it when going down hills. Will watch out for hesitation symptoms with the small amount of driving I do in the UK. Throttle body cleaned not so long ago. 

[Newbie1]

I would be surprised if E10 (10% ethanol, 90% petroleum) would affect a relatively modern engine like the UZ with an ECU that will accommodate a variety of combustion scenarios. However, an issue I had with one car that I modified was ethanol fuels destroying fuel hoses. These were new fuel hoses that were supposedly ethanol safe but that turned out not the be the case. As it happened the number of suppliers of truly ethanol safe fuel hoses was quite small.