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Upon purchase of my used 2013 LS460 I had change the engine oil and filter using Amsoil Signature Synthetic 0W-20. I also filled up the tank with gas then proceeded on a 200 mile road trip. The vehicle was hesitating and bogging down the entire trip as if the timing was retarding. I originally attributed it to bad gas as the symptoms resolved after about a week or so after I had put filled up with a second tank of fuel and added some Star Tron fuel cleaner. After about a week or so the vehicle returned to normal. Now fast forward 10,000 miles later and I just performed another oil change with the same Amsoil 0W-20 and the same issue has arisen. Does anyone know the exact reason for this and what is the work around? I have never heard of engine oil changing the timing characteristics. Any info on the topic will be helpful!
Upon purchase of my used 2013 LS460 I had change the engine oil and filter using Amsoil Signature Synthetic 0W-20. I also filled up the tank with gas then proceeded on a 200 mile road trip. The vehicle was hesitating and bogging down the entire trip as if the timing was retarding. I originally attributed it to bad gas as the symptoms resolved after about a week or so after I had put filled up with a second tank of fuel and added some Star Tron fuel cleaner. After about a week or so the vehicle returned to normal. Now fast forward 10,000 miles later and I just performed another oil change with the same Amsoil 0W-20 and the same issue has arisen. Does anyone know the exact reason for this and what is the work around? I have never heard of engine oil changing the timing characteristics. Any info on the topic will be helpful!
Thanks
You are correct, the ECU was retarding ignition timing. I've spent hours reading about this issue but no one seems to have found the reason why.
Many of these cars seem to have faulty knock sensing systems. Mine thinks it senses knock after oil changes (like yours), and also sometimes at light cruise (~30 mph). The official cause according to Lexus is worn valve guides, and they would replace the cylinder heads on some engines under warranty. However, people with near-new cars have complained about the hesitation after oil change, and some people have had the cylinder heads replaced and the hesitation has returned, so I don't know if worn valve guides are the cause.
The hesitation occurs because the knock sensors are picking up noise from somewhere and the ECU is interpreting that as engine knock and retarding the ignition timing. At my last oil change I monitored the engine knock using an OBD dongle and app. Immediately after the oil change, I saw the ECU registering knock via the Knock Feedback Value (KFV). The Knock Feedback Value feeds into the Knock Correction Learning Value (KCLV), which is the ECU's long-term knock correction (I assume to account for bad fuel or similar). If the ECU detects too much knock via the Knock Feedback, then the KCLV is reduced, and ignition timing retarded. When KCLV gets too low (below ~15 degrees) the car loses power and is noticeably hesitant.
Sustained periods of low Knock Feedback after oil changes will reduce the KCLV and make the car hesitant. After a bit of driving, the car stops sensing knock, but the ECU has to re-learn and will slowly increase KCLV until no hesitation is felt, hence why it takes a couple of hundred miles or so to get back to normal.
When the throttle is closed, the ECU does not seem to register any knock feedback, so getting on and of the throttle for a few miles seems to prevent the ECU from affecting KCLV, which prevents the hesitation. Normally I would have hesitation after oil changes, but by monitoring Knock Feedback and varying the throttle and revs, I was able to get through an oil change without inducing hesitation (see log below). Not really a fix, but it is a work around I guess.
oldred - This knock was the theory since the beginning of discussing this issue years ago. Seems now we have some data to support it (thanks). I'm one of the ones who do my own oil change and have never experienced this issue. I also have a 2010 model.
I want to mention in addition to your reply, that not only is the ECU and sensor detecting knock, that I believe the engine IS ACTUALLY EXPERIENCING KNOCK. As in pre-ignition. So the engine / ECU is just doing what it is programmed to do. The question is (and this is what we've contemplated), why would the engine be experiencing actual pre-ignition after an oil change? That is the question.
The answer is not clear because some cars do this after an oil change, and some do not.
You are correct, the ECU was retarding ignition timing. I've spent hours reading about this issue but no one seems to have found the reason why.
Many of these cars seem to have faulty knock sensing systems. Mine thinks it senses knock after oil changes (like yours), and also sometimes at light cruise (~30 mph). The official cause according to Lexus is worn valve guides, and they would replace the cylinder heads on some engines under warranty. However, people with near-new cars have complained about the hesitation after oil change, and some people have had the cylinder heads replaced and the hesitation has returned, so I don't know if worn valve guides are the cause.
The hesitation occurs because the knock sensors are picking up noise from somewhere and the ECU is interpreting that as engine knock and retarding the ignition timing. At my last oil change I monitored the engine knock using an OBD dongle and app. Immediately after the oil change, I saw the ECU registering knock via the Knock Feedback Value (KFV). The Knock Feedback Value feeds into the Knock Correction Learning Value (KCLV), which is the ECU's long-term knock correction (I assume to account for bad fuel or similar). If the ECU detects too much knock via the Knock Feedback, then the KCLV is reduced, and ignition timing retarded. When KCLV gets too low (below ~15 degrees) the car loses power and is noticeably hesitant.
Sustained periods of low Knock Feedback after oil changes will reduce the KCLV and make the car hesitant. After a bit of driving, the car stops sensing knock, but the ECU has to re-learn and will slowly increase KCLV until no hesitation is felt, hence why it takes a couple of hundred miles or so to get back to normal.
When the throttle is closed, the ECU does not seem to register any knock feedback, so getting on and of the throttle for a few miles seems to prevent the ECU from affecting KCLV, which prevents the hesitation. Normally I would have hesitation after oil changes, but by monitoring Knock Feedback and varying the throttle and revs, I was able to get through an oil change without inducing hesitation (see log below). Not really a fix, but it is a work around I guess.
Thanks Much for the explanation. What amazes me the most is that there is no ECU update that can alter this behavior for such a high end vehicle. I just wanted to ask about your work around. The part about getting on and off the accelerator to trick the ECU. Can you be more specific about this process?
VAM - What if the vehicle really is experiencing knock, for a reason that has yet been proven? Wouldn't you want it do to what it is supposed to do? I for one would want it to retard and avoid possibly damaging pre-ignition. Ignoring a potential problem would be a horrible work around.
In my time at Toyota, we dedicated our engineering efforts to identify THE ACTUAL ROOT CAUSE of a problem, and to fix that problem only. Probably when even you think deeply about it and express exactly what you mean, you would do the same thing ... fix the actual problem. Generous Motors would just mask it by programming the ECU to act dumb (or some such ridiculous countermeasure). And that's why Generous Motors is where they are ... they build C-R-A-P.
My guess is from Toyota's standpoint after having been there (done that), is that this problem with the 4.6L is super minor, and has not reached a threshold where it is worth their time to spend significant resources to determine the root cause.
It is certainly a challenge ... because a lack of oil when draining cannot be the root cause, because for example, my LS may sit for 3 or 4 weeks without being cranked. My engine gets as dry as an LS engine will get. Yet it will crank up and run like it did the day it drove off the showroom floor. The previous very long thread about this issue is really interesting.
Thanks Much for the explanation. What amazes me the most is that there is no ECU update that can alter this behavior for such a high end vehicle. I just wanted to ask about your work around. The part about getting on and off the accelerator to trick the ECU. Can you be more specific about this process?
The car experiences hesitation when KCLV (long-term knock correction) drops. For KCLV to drop, the ECU needs to see sustained periods of low Knock Feedback (instantaneous knock sensing). When the throttle is closed or the car at idle, Knock feedback returns to normal (-3 deg.) and the pattern the ECU needs to see to reduce KCLV is interrupted.
Have a look at the graph below. When Knock Feedback was steady at -3 deg, KCLV remained stable. However, when Knock Feedback dropped below -4.5 deg. for several seconds, the ECU reduced KCLV. This happened twice in short succession (180-215 seconds on the graph) and the ECU lost 3 degrees of timing. Compare that to the graph I posted earlier showing the oil change where by opening and closing the throttle I did not let the ECU see prolonged periods of low Knock Feedback, and the KCLV remained unaffected.
The graph below is what happens after an oil change, but for a longer period of time. KCLV goes through the floor. I've seen KCLV nearly at zero, and the car was really sluggish and hesitant. Which makes sense if ~30 degrees of ignition timing is being wiped out by the ECU.
You'll also see from ~350-450 seconds some sustained spikes in Knock Feedback Value, and the ECU increased KCLV. This is what happens once the 'knocking' after an oil change stops - the car has to re-learn it is safe to increase ignition timing.
VAM - What if the vehicle really is experiencing knock, for a reason that has yet been proven? Wouldn't you want it do to what it is supposed to do? I for one would want it to retard and avoid possibly damaging pre-ignition. Ignoring a potential problem would be a horrible work around.
In my time at Toyota, we dedicated our engineering efforts to identify THE ACTUAL ROOT CAUSE of a problem, and to fix that problem only. Probably when even you think deeply about it and express exactly what you mean, you would do the same thing ... fix the actual problem. Generous Motors would just mask it by programming the ECU to act dumb (or some such ridiculous countermeasure). And that's why Generous Motors is where they are ... they build C-R-A-P.
My guess is from Toyota's standpoint after having been there (done that), is that this problem with the 4.6L is super minor, and has not reached a threshold where it is worth their time to spend significant resources to determine the root cause.
It is certainly a challenge ... because a lack of oil when draining cannot be the root cause, because for example, my LS may sit for 3 or 4 weeks without being cranked. My engine gets as dry as an LS engine will get. Yet it will crank up and run like it did the day it drove off the showroom floor. The previous very long thread about this issue is really interesting.
FWIW, I don't think the engine is actually knocking - I think the knock sensors are picking up some sort of noise from somewhere. Toyota has actually just done what you accuse GM of doing. Lexus USA issued a TSB where they re-flashed the ECU (I presume they reduced the sensitivity of the knock sensors) and some people found the re-flash stopped their hesitation. So, Toyota has gone to some trouble to rectify the issue, but obviously they have not got to THE ACTUAL ROOT CAUSE, unless of course the actual cause is in fact worn valve guides. But the fact people were reporting hesitation after oil change on near-new cars makes me doubt it's worn valve guides.
I could believe the car was experiencing actual knock if someone proposed a plausible reason why. I'm more inclined to think that exposing the oil pickup during an oil change introduces air into the oil system, causing issues somewhere down the line or something like that (which could be why there are no problems after the car is parked for a while). The previous threads on this topic had lots of speculation but no one was able to identify a cause. I think my logs of Knock Feedback can at least rule of problems with cam timing via VVTI, which is something people were suggesting.
oldred - This knock was the theory since the beginning of discussing this issue years ago. Seems now we have some data to support it (thanks). I'm one of the ones who do my own oil change and have never experienced this issue. I also have a 2010 model.
I want to mention in addition to your reply, that not only is the ECU and sensor detecting knock, that I believe the engine IS ACTUALLY EXPERIENCING KNOCK. As in pre-ignition. So the engine / ECU is just doing what it is programmed to do. The question is (and this is what we've contemplated), why would the engine be experiencing actual pre-ignition after an oil change? That is the question.
The answer is not clear because some cars do this after an oil change, and some do not.
7milesout
My car experiences hesitation after two scenarios 1) - after oil changes, and 2) - after cruising at low revs.
The graph I posted in post #3 was after an oil change, and the graph I posted in post #7 above was highway driving at 60 mph. Why did the car suddenly start pre-ignition in a steady state cruise at ~1,500 RPM? The problem is worse at 30 mph (~1,200 RPM). I can lose 30 degrees of timing in a few blocks, yet other times the car is fine. I run good fuel and when under load the ECU does not register any 'knock', hence why I think the problem is related to noise within the engine rather than actual pre-ignition. Lexus thought it was noise within the engine so replaced the cylinder heads on affected vehicles (obviously not mine though). I've also found that moderate acceleration at low revs is when KCLV increases (also in graph is post #7) - this is when I would expect pre-ignition to occur, not at light throttle openings.
I could replace the cylinder heads as per Lexus, but that would cost more than the car is worth so my work around is to keep revs above ~1,800 RPM using the gear lever. This means 4th gear in town and 7th gear at 60 mph. No hesitation and KCLV is usually about 30 degrees.
Interesting thread. Not very encouraging for someone who is considering moving to a 460 but I can think of a few work arounds for this that may or may not work. I have a suspicion the issue may be DI knock/super knock as it's called that can be inherent to ultra high compression engines at low rpm mid/high load situations
Interesting thread. Not very encouraging for someone who is considering moving to a 460 but I can think of a few work arounds for this that may or may not work. I have a suspicion the issue may be DI knock/super knock as it's called that can be inherent to ultra high compression engines at low rpm mid/high load situations
What you’re describing is LSPI ( low speed preignition). Feels like a hesitation, almost fish biting sensation as the fuel is igniting before it’s supposed to. Perhaps the ls460 is preventing that scenario through the knock sensors and engine timing (because I never felt this sensation in my LS), but the oil change scenario doesn’t make sense to me. That shouldn’t effect this, I would think.
MIne did the after i did my first oil change. Took it to dealer for an ecu update and issues has never happened again. Only time i get a hesitation is coming off a stop and going left. Hit the gas the revs go up but speed is flat for a couple secs than off it goes. Done that since i got the car.
What you’re describing is LSPI ( low speed preignition). Feels like a hesitation, almost fish biting sensation as the fuel is igniting before it’s supposed to. Perhaps the ls460 is preventing that scenario through the knock sensors and engine timing (because I never felt this sensation in my LS), but the oil change scenario doesn’t make sense to me. That shouldn’t effect this, I would think.
The reason I suspect it's related is because of the new oil spec for GDIT engines that were having issues with LSPI due to the turbos and high DCR characteristics being combined with PCV oil. That caused enough of a problem to have the new spec developed, I am not sure if it's the same issue in the 460 but it's what came to mind.
Toyota has actually just done what you accuse GM of doing.
It could be (I doubt it), but there's no way to KNOW that, unless we had a mole at Toyota.
Originally Posted by oldred
Lexus USA issued a TSB where they re-flashed the ECU (I presume they reduced the sensitivity of the knock sensors) and some people found the re-flash stopped their hesitation. So, Toyota has gone to some trouble to rectify the issue, but obviously they have not got to THE ACTUAL ROOT CAUSE,
It could be, but there's no way to KNOW that, unless we had a mole at Toyota.
Originally Posted by oldred
But the fact people were reporting hesitation after oil change on near-new cars makes me doubt it's worn valve guides.
I agree with that.
Originally Posted by oldred
I'm more inclined to think that exposing the oil pickup during an oil change introduces air into the oil system, causing issues somewhere down the line or something like that (which could be why there are no problems after the car is parked for a while).
Solid reasoning. I can agree with this possibility.
Originally Posted by oldred
The previous threads on this topic had lots of speculation but no one was able to identify a cause. I think my logs of Knock Feedback can at least rule of problems with cam timing via VVTI, which is something people were suggesting.
I can agree with that too. I also do not believe this has anything to do with VVTI and related filtering.
Originally Posted by oldred
My car experiences hesitation after two scenarios 1) - after oil changes, and 2) - after cruising at low revs.
I think your #1 is the mystery hesitation, and your #2 COULD BE actual pre-ignition. The #2 is one of the scenarios where pre-ignition tends to happen. And your c/m to #2 would be the way to overcome that issue ... manually.
Originally Posted by oldred
Lexus thought it was noise within the engine so replaced the cylinder heads on affected vehicles.
You don't know what Toyota thinks. I can tell you from being in the meetings where solutions were discussed and approved, things are VERY complex. Things rarely went the way I figured them to go. At Toyota, there is no solution implemented by a design engineer that came from 1 person's head. You would be floored to know what they go through at times, even for what some may think are easy solutions. This is where I was taught the value of a decision matrix.
Originally Posted by oldred
This means 4th gear in town and 7th gear at 60 mph. No hesitation and KCLV is usually about 30 degrees.
I do a similar thing. Manually place it in 6th around town because I detest the way it tries to get into 8th gear by 8 mph. I exaggerate of course, but you know what I mean. At 60 mph I bump to 7th like you. Interstate I put it in D.
Interesting thread. Not very encouraging for someone who is considering moving to a 460 but I can think of a few work arounds for this that may or may not work. I have a suspicion the issue may be DI knock/super knock as it's called that can be inherent to ultra high compression engines at low rpm mid/high load situations
Knowing what I know now, people looking to buy these cars should put the car on an OBD scanner and check (or have checked by a garage) the KCLV. If KCLV is below 20, the chance of having hesitation issues is much higher and it’s probably worth looking elsewhere. If KCLV is below 15 then definitely walk away.
The 2UR engine in the ISF can also have problems with KCLV. RR racing refers to these cars as ‘KCLV challenged’, apparently they don’t respond to tuning as well as cars with higher KCLV.
I hadn’t heard of DI knock/super knock before. Interesting. Could be something in it. However, everything I read implied super knock was experienced at high load/low RPM, but I experience the problem at low load/low RPM. Have you heard of low load super knock?
I have wondered about a link between the DI system and the hesitation. It would be nice to disable the direct injectors and run port only injection to see if the problem persists. But that would require an aftermarket ECU, dyno time, and $$$$.
Wonder if there is a link between fresh oil and super knock?
06-22-21, 06:13 AM
LS460 Oil change/ Retarded timing issue
