Hello,

Trying to diagnose partners gs460.
Main question is - do cars with valve guide issues get it intermittently or at certain rpm only?

Reason is it will be sluggish rolling into throttle through multiple gears at times (manual or auto mode), but if left to 'decelerate through a gear in manual and floored at 3.5-4k it'll haul *** and push you back in teh seat like normal through 2nd, 3rd etc. Occasionally it will be slow up a hill. But not near as bad as before the tensioner..
So we are thinking it's two issues manifesting as one end problem.

Since doing tensioner pulley it ran amazingly (efficiency way up, no hesitation, no issues). After a week or two I had the stupid idea of pulling the battery to reset ECU in case there was something left on the table. After that, It then sometimes hesitated and slowly accelerated like when it pulled power due to knock sensing the tensioner noise. But the tensioner is new and this only happened again after pulling battery out.
Going to pull battery again and see if it fixes it..

 

it's not certain RPM's only. When it happens you can floor it and power is loss throughout the entire RPM range. Sometimes you think its certain RPM's only because the knock sensor backs off and give you that power back, but in reality it's always detecting the knock and just how severe that knock is.

 

Thanks for the reply - that matches what happens but it's only sometimes e.g. weeks with it acting normally. It's pretty random really.
But then you can have it go slow in S mode if you slowly roll the gas on but almost never if you floor it suddenly. I would have figured just like with the tensioner, when it detects knock that behavior is pretty constant and goes on for the entire drive. It's similar behavior to tensioner knock pulling but very, very random.
Are the valve guides a pain to press out if it is the guide wear causing it? Has anyone DIY'd it?

edit: better way to ask is - are there any easier ways to get used heads from later model (fixed) 460s or a site that rebuilds them that isn't 1100 USD per head lol.

 

I never knew the valves guides were an issue on the GS460's? If it has worn valve guides more likely you will see a lot of oil burning out of the tail pipes and eventually destroying the valve seals. Then your motor will lose oil almost instantly. Is it losing a lot of oil? Maybe you meant the VVTI, if so then yes at different rpms the car can act slouchy, and the cam gear will make noises. But you said it started after you disconnected the battery.

When you was the last time you replaced or did these kinds of maintenance on the car? If not I would do all of these, more importantly are the plugs.

1. Spark plugs? using oem from a reputable dealer and not fakes off ebay or amazon
2. Air filter
3. Throttle body cleaning? By removing the throttle body and cleaning it thoroughly by pushing the butterfly and cleaning the back side
4. Top engine cleaning? Running seafoam through the intake manifold while the engine is idling through a vacuum line

 

I wouldn't immediately jump to suspecting valve guides as a potential issue, but a valve guide issue would not manifest the way you are describing. at the point that a valve guide has gone bad enough to cause a noticeable driveability issue you would be hearing a whole lot of horrible noises and or dragging compression on the effected cylinder. Also knock sensors are only pick up a very narrow range of frequency, a tensioner being loose (which these days is very uncommon in the first place since modern tensionrs generally last the life of the car) will not register with a knock sensor.

What was the reason you replaced the tensioner in the first place?

Pulling the battery can sometimes have some oddball effects with adaptive learning on the engine management, I would just keep driving it normally to see if the computer figures itself out before I went changing anything else.

 

Thanks for that peace of mind. Definitely no nasty noises, it sounds like a perfectly made industrial sewing machine on each cylinder, I listen to it most mornings when she goes as I'm paranoid after a dead F20C in my past. Main effect that is obvious from all this is efficiency drops when it's unhappy, it's the main problem aside from lower power output. Have got 10-12km/L out of the car average for two weeks (little higher than average MPG and record for this car) after tensioner was done, before pulling battery... whoops. Now it's 7.7-9 range, but behaving much better on average than pre-tensioner driveability - no poor pulling out/hunting/hesitating for gears/pulling so much power its hard to go up hills etc).
Lowest efficiency is significantly low when it 'pulls power' on rare occasion usually 2nd-3rd under light to medium accel (3-5km/L instantaneous). If continuing through rev range it will increase speed now but nothing like what it should under full throttle.

>Pulling the battery can sometimes have some oddball effects with adaptive learning on the engine management, I would just keep driving it normally to see if the computer figures itself out before I went changing anything else.
Been well over a month now with 3 weeks of regular driving and some 'using in anger S/D mode' on occasions to see if it'd learn properly hence considering a battery pull.

Tensioner was replaced ~2 months ago. Another member here had exact same issue and similar results but it appeared to fix it for good, unlike this post-battery pull. Bearing was very stiff and making the sometimes embarrassingly loud/variable whistling noise, made the car run terribly retarded timing often (almost always was 'slow' and low efficiency at most speeds), took a few months of careful observation but correlation was there when watching it pull timing on Torque app and matching symptoms with tensioner noise. Tensioner also had been pulled apart before by some muppet, with some tape put in the spring and it had broken plastic guides, so it wasn't holding straight nor performing well regardless of the bearing issues. Terrible bodge job for a cheap/easy to change part, it was infuriating to see that on such a beautiful piece of engineering.

If it matters it's an 07' JDM GS460 ~80-90k miles/130~km. There are no major outstanding service recalls etc according to Lexus and the 2? main ones were done.
No codes but I don't trust Torque so considering bringing it to Lexus here.
Reason I went down this track is it seems like two issues causing power pulling (base behaviour is similar) hence suspecting guides being worth digging as I didn't realise they would be loud when showing symptoms, figured this was just a super sensitive modern engine so thanks for the heads up on knock sensors.


https://www.clublexus.com/forums/att...celeration.pdf
http://carspecmn.com/ls460-and-ls600...g-andor-p2119/
460 but for LS/GX, don't see how/why it wouldn't apply to GS.

After tensioner replacement, efficiency shot up 20-30% for two weeks (record efficiency) until pulling battery when power pulling behavior came back but not near as bad as pre-tensioner pulling.
She's only had the car for 6-7 months, It burns oil like any other 1UR but well within the limits Lexus sets for consumption, e.g. might need 1L or so topped up between each change.
It will smoke/dust carbon out first few times giving it the boot if it's been driven lazily for a few days/weeks (will make excess carbon when pulling timing too...) but after that will run clean at max load, including being right behind it during this with lights on. No smoke/smell on cold start just condensation as usual. Does make 'cat smell' when you floor it first few times but clears out mostly after that until next commute period.
This is also why I dismissed the valve guide issue when mrs bought it up until learning it was more mechanical noise from tapping. I have a 5sfe with slightly worn guides that I daily which isn't loud though.

1: Plugs are next on the list of things to inspect and trans plug/cable inspection/clean.
2: Filter is pretty clean
3: TB is good suggestion as have heard of some issues regarding it before. Have inspected it recently when doing tensioner and it was pretty clean though.
4: Top end clean is a good idea too. Have used injector cleaner already, it made a small improvement in economy but this was when tensioner was causing power pulling (and very bad vs now).

 

I would start by removing and cleaning the throttle body inside and out. Aswell as the maf sensor! Just because an air filter looks clean doesnt mean its not clogged up. If you have an old clogged air filter it will for sure kill your performance. But I think your issue is from the spark plugs, replace with oem or ngk from a reputable seller like rockauto.com etc.

But before you swap out the plugs, I would get the engine nice and hot and do a top engine cleaning. You will need to buy a can of seafoam (the pour kind is best) or better BG, and a vacuum hose. Pop off the engine cover and look for a blank capped off vacuum plug on the intake manifold. Remove the clamp, plug and install the vacuum hose and with the engine nice and hot soaked start the car and let it idle. Pour 1/3 cup of cleaner into a cup and let the vacuum from the hose drink the cleaner. Feed it just enough solution to give that idle a little stumble, but not too much to where it stalls on you. You will get a ton of smoke coming out of the exhaust that is normal. Finish the 1/3 cup, turn off the engine and let it rest for 30min this will allow the chemical to soak into the carbon. Just keep repeating until you complete the full bottle. Put back on the vacuum plug! Take it on the highway and drive it hard. Swap out the spark plugs, and enjoy your new performance.

 

It is most likely the valve guide. The MAF sensors don't get dirty easily, they are specially coated. Also if you look at the throttle body, it should be very clean.

I would not waste time on it, including using fuel injector cleaners or engine additives to clean the engine. I would simply plug TechStream and look at the Knock values as indicated by the TSB. If the Knock values are abnormal, it's not worth fixing the car, the job is too big. Unless you really love the car and want to keep it forever.

 

Looks like you might be bang on the mark... They're not so pretty!
Plugs are pretty dirty. Plugs pulled were front and 3nd from front on drivers side bank (we are RHD) (sorry couldn't find cylinder numbering diagram easily it's not an LS ).
Looks like too much timing but bit rich down low? Not a plug expert but that 2nd plug with the large gap will definitely be causing issues, hence it has most residue wicking up. 14ft/lbs also seems pretty loose!

Also went for a drive to monitor timing. When it pulled timing and made low power/slow acceleration it was down to -14° and when it made power it put more timing in. Highest timing was 46° when letting off the throttle after a power run!! Bit too high surely?
Under load when it was not pulling so much timing (seems rpm dependent) it was running 5-10° and under full throttle (when pulling good) 10-14° maybe up to 20 if letting off a little. The timing increase with a constant throttle percentage was interesting, as it increased gradually the power increased going up a hill with constant throttle. Basically higher the timing the better the economy. Under low rpm and low load the timing goes really far negative.

Now I'm really curious if the plugs have been touched at all. I wouldn't expect plug 1 to be so worn in what is less than 1/3rd of the lifetime.. or have they never been changed? They look like an old model. That said, if it was running hellishly rich from the tensioner causing knock sensor to trigger, then maybe it caused all the issues we have now.
Thanks for the help we will be ordering new plugs tonight and some seafoam/top end cleaner locally available.


End of plug 1 marking (plug 2 identical)

plug one, gap not as worn as #2, not too wet threads

plug 1

plug 1

plug 2 on left, note much more wear on electrodes (gone) and more oil/fuel wicking

plug 2 left

plug 2 left

 

Hard to say without a techstream. Torque doesn't pick up knock values or any error messages just some of the realtime data.
I think if it was knock it would be more audible and consistently with a persistent issue and never make good power when it's behaving. Plugs are shot so definitely worth looking at. Maf pictures attached, definitely dirtier on one side than the other.. Lexus tech said above that timing is quite audible and wouldn't have the symptoms I had. But who knows. Will clean it out, do plugs and see because as it is it's only sometimes unhappy it's still usable and bearable.





inlet side dirtier

 

Ya those plugs are toast! That maf is dirty aswell! Maybe those plugs are fakes, and not true iridium. I think the ecu pulled back timing because of the plugs to compensate the tune. Once you clean the throttle body and do that induction cleaning she should run like a champ. Let us know how she runs after you finish

 

Remember it’s not actually knock, it’s just the sound sensor thinking it’s knock, so starts retarding the timing. You can’t actually hear any difference.

All Toyota and Lexus tech should have access to Techstream. You can also get a few day subscription to Techstream via TIS.

 

Thanks so much for the heads up
Edit: Checked extensively and learned lots about fake vs real plugs, they almost certainly real plugs going by the printing on the side of the metal ring and other aspects. The end stamps on the contact point may show they are original/factory fitted as they don't come on retail plugs... Which means they have never been changed... BUT they are this way at 83k miles not 100k! I find that interesting. Other alternative is they are the best fakes I have ever seen and only 20k miles old. So I'd say probably the result of 10s of thousands of kms driving with a bad tensioner pulling power (tensioner made a massive difference to drive-ability, now it's just efficiency being low). That said the ***** fake plugs are usually chewing the base electrode to round, where as the above plug electrodes are (relatively - vs fake plugs of low mileage) fine and the top electrode is gone instead... Can also see clearly the laser soldered iridium 'lumps'. Fakes don't bother with them.
Very curious if anyone has seen the end markings on the plugs before.

Will be using acetone + cotton bud to gently clean the MAF (much cheaper than paying 20 dollars for a can of compressed gas and some acetone lol).

Seen some mention oil changes after top end cleaning (we can't get seafoam in NZ, instead will try CRC valve cleaner or similar, other option is AC Delco clone of Seafoam (rebrand) if here). Apparently the solvents that remove the carbon can impact oil and some recommend changing it after. Oil was changed 3500km ago.. and it's not exactly cheap on a 460 - wondering if we can just do a top up as the cars they were mentioning changing it on have about half the oil capacity of our 460s (thus more susceptible to oil impact).


Yeah you don't have to hear it - same issue as was happening with the tensioner noise triggering knock sensors. They are sensitive things it seems. Lextech above said though that when they are actually valve guide related issues it is audible to them. Will get this stuff done and if issues continue it'll be off to lexus. At least it'll help solve some problems for now.

 

Ya fake plugs can easily trick a person into thinking they are real. Especially with the high price of the oem/ngk plugs, when someone hops on ebay or amazon and sees oem plugs for his car in an original looking boxes for a 10th of the price. They jump on it!

CRC is nice, but its pretty pricey! Acdelco is a good option, but I hear mopar combustion cleaner is very good. So maybe if you have a local dodge/jeep dealer check with them. I wouldnt be concerned about the chemical contaminating the oil, because you will run it through the intake combustion. The chemical will atomize and burn. For the Maf not sure how strong acetone is, but maybe safer to go with something milder like rubbing alcohol or an electronic spray cleaner with a cotton buds. Maf is pretty sensitive! Dont forget to the throttle body aswell, and air filter.

 

Those low prices are enticing but you have to get a general feel for the market first. What I did this time was check what all the reputable, real stores had the plugs for. Rock auto was a bit more cost than the cheapest but it was the only one that could handle customs charges and international shipping without having to personally do the deal with customs muppets to pay some money part. There were some UK which were walmart cheap but no pre-shipping GST so it wasn't worth the hassle. Also rockauto has the best rep..


I've used acetone a lot in my industry as it's residue free so will be fine for electronics or similar or metal alone. I'll use rubbing alc on the resistors? in closer proximity (high vapour amount). And you raise a good point - for those considering using it, I'll keep acetone away from the mounting plastic (or do a test spot ), it'll do well for throttle body cleaning as well with same caveats for rubber and plastic at minimum.

CRC cans are pricey. Gallon jugs of WD40 are better, unfortunately it won't do the same job as a decent GDI cleaner .
Also seen a recipe for Seafoam by some chemical geek MSDS-reading legend;
4 parts diesel
2 parts naphtha
1 part IPA