roadfrog

It does if you read the posts by Devh. Based on the limited reading I've done, there's abundant info about how the VVT-I system as well as Direct Injection engines work and how the use of the correct oils contribute to proper operation.

As I stated, my oil consumption dropped, and my oil analysis reports show much, much better results ( far lower levels of several chemicals and deposits) compared to my previous uses of other oils, even with highly regarded oils such as Pennzoil Ultra Premium which BITOG rave about.

SW17LS

I've never owned a Lexus that consumed any oil, even upwards of 200k miles so I wouldn't be looking for oil consumption to drop...

caha14

I believe the number that has been stated as "normal" (by sources ranging from reliable to "hearsay") for the LS460 is up to a quart in between oil changes (5,000-mile interval). Personally, I had zero noticeable consumption in my 460. Some folks have more moderate consumption and a handful of folks (on CL) reported bigger issues post-valve spring recall.

Having said this, the original cause of the more common hesitation had to do with knock sensors being triggered by noise unrelated to knock, retarding timing and killing power. In my case, a software update (per TSIB) fixed the problem. In others' cases, new cylinder heads did the trick (per the same TSIB). I can't remember specifics, but apparently an out-of-tolerance component in the valve train could lead to additional wear, exacerbating noise, knock sensors kicking in, etc.

Fourth-gen LS hesitation has been an enigma not only for LS460 owners, but also for Lexus and dealerships. For instance, as of 2011, when my 460 was fixed, they were already on the 5th version of calibration software, chasing - among other things - the hesitation problem. My engine had no mechanical problems, yet somehow, all it took was a new battery and my wife driving the car one time for the hesitation to begin and for the car to put me in dangerous situations more than once. Evidently, there was something that the ECU was learning that it wasn't supposed to.

At any rate, I never suffered post-oil-change hesitation. However, I was doing oil changes at the dealership with Toyota oil. What is interesting is that I vaguely remember reading of some folks on here who HAVE experienced this even after an oil change at the dealership. On the other hand, roadfrog's experience is very revealing, and the findings he reports have been similar at my dealership (where I've had lengthy conversations on the subject with the Diag Specialist). Findings at the dealership go beyond brand into viscosity, where use of other allowed weights (at least for '07-'09) further exacerbated hesitation.

What is at play, specifically, is unclear. I also hear you that VVTi is VVTi, irrespective of application across models. However, there does seem to be something unique about the system in this 4.6L (and the 5.0L on the 600), at least in the earlier vintages. It's as if only certain oils are flowing quickly enough to all the right places after an oil change.

Devh

Since my name was mentioned I better reiterate my explanation.

These VVT systems rely on the engine oil as a hydrolic function and that is why the Toyota oil in it's grade is better suited for this application because of the tightness of the passages. It doesn't mean that you cant use other oil but it may not be optimal.

What Roadfrog experienced is a typical problem experienced with VVT systems if you change from Dino oil to Synthetic. There are deposit that get cleaned out anytime you change to synthetic oil which get's suspended and then trapped by the VVT screens. The hesitation goes away once the deposits liquefy by the detergent action of the oil. The hesitation is due to a loss of oil pressure in the area that controls the VVT. This cycle will continue every time you do an oil change until the depots are cleaned out by synthetic oil or the process can be expedited using a gentle flush or additive.

Doublebase

One thing to consider, the LS460 is run by a system called vvt-ie, which uses an electric motor to operate the intake cam timing - it is not dependent on oil pressure or engine temperature.

As for the exhaust cam, it is hydraulic, but it is monitored by the sensor on the back of the cam for voltage values that change with engine speed, temperature, TPS position, load, transmission gear, cam position, and many other factors. These systems sense faulty operation very quickly and throw a code that leads to a check engine light..low oil, dirty oil, clogged valve, faulty sensor...would all be monitored and tested at least every fifteen seconds by the ECM. If it were to fail any of it's tests, it would put a check engine light on.

As for VVT-I systems, they run an oil valve and sensor at the intake and exhaust cam. If valve overlap is stuck in it's "normal" position, idle would be clean and consistent, but if it does not adjust the cams after 3k rpm, power will be sluggish (compared to what you are used to). But performance from idle to 3k rpms shouldn't change all that much (if at all in some cases). If the cams are stuck in a larger overlap mode, engine idle will be rough and you'll experience power loss initially, with some misfires, but it actually should be decent at higher rpms.

Road frog's situation seems unique to what I'm going through, from what I've read fuel is the number one culprit to this hesitation issue. I have run TGMO in the past and it hasn't helped my situation at all...and I've never run anything but the proper weight synthetic in this vehicle. I blame myself because I switch between midgrade and Super every other week. Plus I gas up at places that aren't exactly in the same class as Shell or Mobil. What I may do is try a higher grade fuel for a few weeks and see if that helps, but honestly this "problem" is something I can live with, it's not that bad.

If anyone really wants to know if the VVt system is at fault, disconnect the electrical connector in front of the exhaust cam, if it doesn't mimic your problem, then that's not your problem. These systems will drive without it working, so I doubt you'll hurt anything, but don't quote me on that

Devh

Even though the intake came is regulated by an electric motor the exhaust cam as you mentioned is not and is depended on oil pressure. The Oil Control Valves have little screens or strainers that clog up. On many Toyota Engines like my VVTLi it has a major influence and if the screens are clogged as it has happened with owners who have run dino and then synthetic oil experience the same problem with hesitation without a CEL. It's a glitch in the system that is not picked up by the computer for some reason but in most all cases servicing the screens has alleviated the problem.
Roadfrogs problem is no unique as it has effected two other members which also has a history of switching over to synthetic and they were both were remedied in the same manor not to have returned in subsequent oil changes.

There might be many other causes for persistent hesitation but one thing unique about this condition is hesitation after an oil change and then going away after a few hundred miles.

Doublebase

So you're saying the problem occurs only after an oil change, when going from conventional to synthetic?

Then my problem is most likely fuel - I've used synthetic since I've owned it and my hesitation does not occur after an oil change, but rather intermittently once in a while, but it does happen. I'm surprised a PM sensor wouldn't pick the problem up immediately, but like you said, it doesn't happen long.

Devh

Well yes and subsequent oil changes with synthetic oil afterwards until the deposits are cleared out. The detergent component is probably strongest on the initial oil change striping the varnish in chunks rather then liquifying over time.
Some have tripped a CEL once the screens are completely blocked but partially it seems to have an allowance.

roadfrog

My issues did not start when going to synthetics....they started when I used OTHER than TGMO. My Lexus dealer service history shows nothing but TGMO oil changes (0W30). I decided to go with oils (all synthetic), that I bought on sale and have used in other vehicles before. THAT is when the problems started. Immediately after my first oil change using the Pennzoil Ult Dur 0W30 oil I had the hesitation. I immediately came home and did a search here at CL on hesitation and the first thread I found was "hesitation after oil change". I thought, "huh?" ....how can an oil change cause that". As noted by the posts, my hesitation disappeared after about 500 miles. No one really had a handle on why it occurred, so I did my next change with Supertech 0W30 and again immediately felt the hesitation which of course disappeared like everyone else after a few hundred miles. It was then that I got desperate to find a cure and resorted to Rislone Engine Oil Treatment. This decision was based on the theory noted above by my friend Doublebase, regarding our oversensitive knock sensors. Again, I was desperate. Almost immediately after the Rislone, the hesitation completely disappeared. The next change, I used TGMO oW20 after an initial cleaning with the Toyota Oil System Cleaner. As stated, that was about 16k miles ago and on my second TGMO OCI with ZERO hesitation. As I've also stated, the engine oil consumption continues to drop (now at 2k miles on this OCI) and the oil level hasn't dropped on the dipstick. I will add that the engine is smoother and quieter than it's ever been.

Doublebase

Regarding the knock sensors, I was thinking that perhaps worn valve guides caused a little chatter in your engine, engaging the knock sensors. But that was only after I read the head replacement thread...plus you had that oil consumption issue (which I though could have been worn valve guides).

Glad you have solved your problems with something as simple as oil. I imagine your oil consumption issue may have been dirty oil rings that have slowly been clearing up with the TGMO, but then again you say it's been run on that for most of it's life. Either way you are out of the woods.

My problem - and I don't really consider it a problem - is that the car hesitates upon acceleration. It take a moment to kind of get going. It's almost a lag...followed by a response. It doesn't do it all the time, but it does do it. I have run TGMO and it still did it with it in there...and it's not a, right after an oil change thing. It doesn't care when I have the oil changed, it still does it. And my engine is very tight, it burns almost zero oil, yet it will delay on acceleration for a couple seconds once in a while. Like I said, it's no big deal and I'm beginning to think it's the quality - or lack of quality - fuel I'm putting in it. I think I'm affecting the combustion process just a little bit by switching between mid grade and super. I'm going to run straight super for a few weeks and see if that handles it.

Devh

Are you sure it wasn't Toyota semi synthetic oil because that is sold as a 30wt oil. Toyota never pushed the Synthetic oil until recently. According to my records my oil changes from the previous owner was just regular Toyota oil and I have seen it in the Toyota bottle at the dealership.
The dealerships back then were not changing the oil to Synthetic on a regular service unless it was requested.

caha14

Valve guides, that's it! Posted about them triggering knock sensors, some years ago, but could not remember in my earlier post.

Not sure if you've answered this elsewhere; I assume you've done the calibration update? My car did not need heads, and this update transformed it into a different car.

The hesitation that almost got my car rear-ended was all gone, though I did occasionally experience weird lags as well. I always pumped Shell V-Power, and a bottle of Techron every now and then worked like a charm (something worth considering).

Doublebase

I don't know if my car has been updated with the new calibration, is that covered as a recall/warranty?

I hear once it's done there's no going back, so I think I'll try the better fuel first to see if it helps. Like I said it's not drastic, but sometimes I do fear..I'm going to get rear ended, but then it kicks in. So the flash works?

caha14

It works like a charm!

As a bit of context, I was the first one done at my dealership several years ago (and likely one of the earlier folks on CL to post about it. At the time, because of irreversibility, as you state, and the history with updates to the ES330 and RX330 (that didn't work all that well in some cases), they were reluctant (for those cars, interestingly, premium fuel made a huge difference).

I convinced them, especially after describing how I had my foot to the floor and had some nincompoop in a little 4-cyl car riding my tail beeping at me! The shop foreman was blown away by the results, and their view that these flashes were all bad was forever erased I was amazed as well.

The work was covered by TSIB L-SB-0033-08, which I don't have handy at the moment but can post (may have even posted elsewhere in the past, and others have posted it too). For reference, my late-2007-build 2008 was outdated by two or three versions of the calibration, so if this has never been done to your car, you likely have one of the first couple versions.

The applicable warranty is powertrain, which you are likely still out of, but if you have a good relationship with your dealership, this is hardly a labor-intensive job. Yes, it takes time, but the bulk of it is the car sitting pretty with the Techstream uploading to it.

roadfrog

I just went to have another look at my service history. It's been a while since I looked at it. So as it turns out, it shows as 5W20 since the day it was delivered.

Any thoughts?